linux-stable/fs/binfmt_misc.c

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/*
* binfmt_misc.c
*
* Copyright (C) 1997 Richard Günther
*
* binfmt_misc detects binaries via a magic or filename extension and invokes
* a specified wrapper. See Documentation/binfmt_misc.txt for more details.
*/
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/magic.h>
#include <linux/binfmts.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/string_helpers.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/syscalls.h>
#include <linux/fs.h>
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
#include <linux/uaccess.h>
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
#ifdef DEBUG
# define USE_DEBUG 1
#else
# define USE_DEBUG 0
#endif
enum {
VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
};
static LIST_HEAD(entries);
static int enabled = 1;
enum {Enabled, Magic};
#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
#define MISC_FMT_OPEN_BINARY (1 << 30)
#define MISC_FMT_CREDENTIALS (1 << 29)
typedef struct {
struct list_head list;
unsigned long flags; /* type, status, etc. */
int offset; /* offset of magic */
int size; /* size of magic/mask */
char *magic; /* magic or filename extension */
char *mask; /* mask, NULL for exact match */
char *interpreter; /* filename of interpreter */
char *name;
struct dentry *dentry;
} Node;
static DEFINE_RWLOCK(entries_lock);
static struct file_system_type bm_fs_type;
static struct vfsmount *bm_mnt;
static int entry_count;
binfmt_misc: expand the register format limit to 1920 bytes The current code places a 256 byte limit on the registration format. This ends up being fairly limited when you try to do matching against a binary format like ELF: - the magic & mask formats cannot have any embedded NUL chars (string_unescape_inplace halts at the first NUL) - each escape sequence quadruples the size: \x00 is needed for NUL - trying to match bytes at the start of the file as well as further on leads to a lot of \x00 sequences in the mask - magic & mask have to be the same length (when decoded) - still need bytes for the other fields - impossible! Let's look at a concrete (and common) example: using QEMU to run MIPS ELFs. The name field uses 11 bytes "qemu-mipsel". The interp uses 20 bytes "/usr/bin/qemu-mipsel". The type & flags takes up 4 bytes. We need 7 bytes for the delimiter (usually ":"). We can skip offset. So already we're down to 107 bytes to use with the magic/mask instead of the real limit of 128 (BINPRM_BUF_SIZE). If people use shell code to register (which they do the majority of the time), they're down to ~26 possible bytes since the escape sequence must be \x##. The ELF format looks like (both 32 & 64 bit): e_ident: 16 bytes e_type: 2 bytes e_machine: 2 bytes Those 20 bytes are enough for most architectures because they have so few formats in the first place, thus they can be uniquely identified. That also means for shell users, since 20 is smaller than 26, they can sanely register a handler. But for some targets (like MIPS), we need to poke further. The ELF fields continue on: e_entry: 4 or 8 bytes e_phoff: 4 or 8 bytes e_shoff: 4 or 8 bytes e_flags: 4 bytes We only care about e_flags here as that includes the bits to identify whether the ELF is O32/N32/N64. But now we have to consume another 16 bytes (for 32 bit ELFs) or 28 bytes (for 64 bit ELFs) just to match the flags. If every byte is escaped, we send 288 more bytes to the kernel ((20 {e_ident,e_type,e_machine} + 12 {e_entry,e_phoff,e_shoff} + 4 {e_flags}) * 2 {mask,magic} * 4 {escape}) and we've clearly blown our budget. Even if we try to be clever and do the decoding ourselves (rather than relying on the kernel to process \x##), we still can't hit the mark -- string_unescape_inplace treats mask & magic as C strings so NUL cannot be embedded. That leaves us with having to pass \x00 for the 12/24 entry/phoff/shoff bytes (as those will be completely random addresses), and that is a minimum requirement of 48/96 bytes for the mask alone. Add up the rest and we blow through it (this is for 64 bit ELFs): magic: 20 {e_ident,e_type,e_machine} + 24 {e_entry,e_phoff,e_shoff} + 4 {e_flags} = 48 # ^^ See note below. mask: 20 {e_ident,e_type,e_machine} + 96 {e_entry,e_phoff,e_shoff} + 4 {e_flags} = 120 Remember above we had 107 left over, and now we're at 168. This is of course the *best* case scenario -- you'll also want to have NUL bytes in the magic & mask too to match literal zeros. Note: the reason we can use 24 in the magic is that we can work off of the fact that for bytes the mask would clobber, we can stuff any value into magic that we want. So when mask is \x00, we don't need the magic to also be \x00, it can be an unescaped raw byte like '!'. This lets us handle more formats (barely) under the current 256 limit, but that's a pretty tall hoop to force people to jump through. With all that said, let's bump the limit from 256 bytes to 1920. This way we support escaping every byte of the mask & magic field (which is 1024 bytes by themselves -- 128 * 4 * 2), and we leave plenty of room for other fields. Like long paths to the interpreter (when you have source in your /really/long/homedir/qemu/foo). Since the current code stuffs more than one structure into the same buffer, we leave a bit of space to easily round up to 2k. 1920 is just as arbitrary as 256 ;). Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-13 22:52:03 +00:00
/*
* Max length of the register string. Determined by:
* - 7 delimiters
* - name: ~50 bytes
* - type: 1 byte
* - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
* - magic: 128 bytes (512 in escaped form)
* - mask: 128 bytes (512 in escaped form)
* - interp: ~50 bytes
* - flags: 5 bytes
* Round that up a bit, and then back off to hold the internal data
* (like struct Node).
*/
#define MAX_REGISTER_LENGTH 1920
/*
* Check if we support the binfmt
* if we do, return the node, else NULL
* locking is done in load_misc_binary
*/
static Node *check_file(struct linux_binprm *bprm)
{
char *p = strrchr(bprm->interp, '.');
struct list_head *l;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Walk all the registered handlers. */
list_for_each(l, &entries) {
Node *e = list_entry(l, Node, list);
char *s;
int j;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Make sure this one is currently enabled. */
if (!test_bit(Enabled, &e->flags))
continue;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Do matching based on extension if applicable. */
if (!test_bit(Magic, &e->flags)) {
if (p && !strcmp(e->magic, p + 1))
return e;
continue;
}
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Do matching based on magic & mask. */
s = bprm->buf + e->offset;
if (e->mask) {
for (j = 0; j < e->size; j++)
if ((*s++ ^ e->magic[j]) & e->mask[j])
break;
} else {
for (j = 0; j < e->size; j++)
if ((*s++ ^ e->magic[j]))
break;
}
if (j == e->size)
return e;
}
return NULL;
}
/*
* the loader itself
*/
static int load_misc_binary(struct linux_binprm *bprm)
{
Node *fmt;
struct file *interp_file = NULL;
char iname[BINPRM_BUF_SIZE];
const char *iname_addr = iname;
int retval;
int fd_binary = -1;
retval = -ENOEXEC;
if (!enabled)
goto ret;
/* to keep locking time low, we copy the interpreter string */
read_lock(&entries_lock);
fmt = check_file(bprm);
if (fmt)
strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
read_unlock(&entries_lock);
if (!fmt)
goto ret;
syscalls: implement execveat() system call This patchset adds execveat(2) for x86, and is derived from Meredydd Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528). The primary aim of adding an execveat syscall is to allow an implementation of fexecve(3) that does not rely on the /proc filesystem, at least for executables (rather than scripts). The current glibc version of fexecve(3) is implemented via /proc, which causes problems in sandboxed or otherwise restricted environments. Given the desire for a /proc-free fexecve() implementation, HPA suggested (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be an appropriate generalization. Also, having a new syscall means that it can take a flags argument without back-compatibility concerns. The current implementation just defines the AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be added in future -- for example, flags for new namespaces (as suggested at https://lkml.org/lkml/2006/7/11/474). Related history: - https://lkml.org/lkml/2006/12/27/123 is an example of someone realizing that fexecve() is likely to fail in a chroot environment. - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered documenting the /proc requirement of fexecve(3) in its manpage, to "prevent other people from wasting their time". - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a problem where a process that did setuid() could not fexecve() because it no longer had access to /proc/self/fd; this has since been fixed. This patch (of 4): Add a new execveat(2) system call. execveat() is to execve() as openat() is to open(): it takes a file descriptor that refers to a directory, and resolves the filename relative to that. In addition, if the filename is empty and AT_EMPTY_PATH is specified, execveat() executes the file to which the file descriptor refers. This replicates the functionality of fexecve(), which is a system call in other UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and so relies on /proc being mounted). The filename fed to the executed program as argv[0] (or the name of the script fed to a script interpreter) will be of the form "/dev/fd/<fd>" (for an empty filename) or "/dev/fd/<fd>/<filename>", effectively reflecting how the executable was found. This does however mean that execution of a script in a /proc-less environment won't work; also, script execution via an O_CLOEXEC file descriptor fails (as the file will not be accessible after exec). Based on patches by Meredydd Luff. Signed-off-by: David Drysdale <drysdale@google.com> Cc: Meredydd Luff <meredydd@senatehouse.org> Cc: Shuah Khan <shuah.kh@samsung.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rich Felker <dalias@aerifal.cx> Cc: Christoph Hellwig <hch@infradead.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 00:57:29 +00:00
/* Need to be able to load the file after exec */
if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
return -ENOENT;
if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
retval = remove_arg_zero(bprm);
if (retval)
goto ret;
}
if (fmt->flags & MISC_FMT_OPEN_BINARY) {
/* if the binary should be opened on behalf of the
* interpreter than keep it open and assign descriptor
* to it
*/
fd_binary = get_unused_fd_flags(0);
if (fd_binary < 0) {
retval = fd_binary;
goto ret;
}
fd_install(fd_binary, bprm->file);
/* if the binary is not readable than enforce mm->dumpable=0
regardless of the interpreter's permissions */
would_dump(bprm, bprm->file);
allow_write_access(bprm->file);
bprm->file = NULL;
/* mark the bprm that fd should be passed to interp */
bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
bprm->interp_data = fd_binary;
} else {
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
}
/* make argv[1] be the path to the binary */
retval = copy_strings_kernel(1, &bprm->interp, bprm);
if (retval < 0)
goto error;
bprm->argc++;
/* add the interp as argv[0] */
retval = copy_strings_kernel(1, &iname_addr, bprm);
if (retval < 0)
goto error;
bprm->argc++;
exec: do not leave bprm->interp on stack If a series of scripts are executed, each triggering module loading via unprintable bytes in the script header, kernel stack contents can leak into the command line. Normally execution of binfmt_script and binfmt_misc happens recursively. However, when modules are enabled, and unprintable bytes exist in the bprm->buf, execution will restart after attempting to load matching binfmt modules. Unfortunately, the logic in binfmt_script and binfmt_misc does not expect to get restarted. They leave bprm->interp pointing to their local stack. This means on restart bprm->interp is left pointing into unused stack memory which can then be copied into the userspace argv areas. After additional study, it seems that both recursion and restart remains the desirable way to handle exec with scripts, misc, and modules. As such, we need to protect the changes to interp. This changes the logic to require allocation for any changes to the bprm->interp. To avoid adding a new kmalloc to every exec, the default value is left as-is. Only when passing through binfmt_script or binfmt_misc does an allocation take place. For a proof of concept, see DoTest.sh from: http://www.halfdog.net/Security/2012/LinuxKernelBinfmtScriptStackDataDisclosure/ Signed-off-by: Kees Cook <keescook@chromium.org> Cc: halfdog <me@halfdog.net> Cc: P J P <ppandit@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-20 23:05:16 +00:00
/* Update interp in case binfmt_script needs it. */
retval = bprm_change_interp(iname, bprm);
if (retval < 0)
goto error;
interp_file = open_exec(iname);
retval = PTR_ERR(interp_file);
if (IS_ERR(interp_file))
goto error;
bprm->file = interp_file;
if (fmt->flags & MISC_FMT_CREDENTIALS) {
/*
* No need to call prepare_binprm(), it's already been
* done. bprm->buf is stale, update from interp_file.
*/
memset(bprm->buf, 0, BINPRM_BUF_SIZE);
retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
} else
retval = prepare_binprm(bprm);
if (retval < 0)
goto error;
retval = search_binary_handler(bprm);
if (retval < 0)
goto error;
ret:
return retval;
error:
if (fd_binary > 0)
sys_close(fd_binary);
bprm->interp_flags = 0;
bprm->interp_data = 0;
goto ret;
}
/* Command parsers */
/*
* parses and copies one argument enclosed in del from *sp to *dp,
* recognising the \x special.
* returns pointer to the copied argument or NULL in case of an
* error (and sets err) or null argument length.
*/
static char *scanarg(char *s, char del)
{
char c;
while ((c = *s++) != del) {
if (c == '\\' && *s == 'x') {
s++;
if (!isxdigit(*s++))
return NULL;
if (!isxdigit(*s++))
return NULL;
}
}
s[-1] ='\0';
return s;
}
static char *check_special_flags(char *sfs, Node *e)
{
char *p = sfs;
int cont = 1;
/* special flags */
while (cont) {
switch (*p) {
case 'P':
pr_debug("register: flag: P (preserve argv0)\n");
p++;
e->flags |= MISC_FMT_PRESERVE_ARGV0;
break;
case 'O':
pr_debug("register: flag: O (open binary)\n");
p++;
e->flags |= MISC_FMT_OPEN_BINARY;
break;
case 'C':
pr_debug("register: flag: C (preserve creds)\n");
p++;
/* this flags also implies the
open-binary flag */
e->flags |= (MISC_FMT_CREDENTIALS |
MISC_FMT_OPEN_BINARY);
break;
default:
cont = 0;
}
}
return p;
}
/*
* This registers a new binary format, it recognises the syntax
* ':name:type:offset:magic:mask:interpreter:flags'
* where the ':' is the IFS, that can be chosen with the first char
*/
static Node *create_entry(const char __user *buffer, size_t count)
{
Node *e;
int memsize, err;
char *buf, *p;
char del;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: received %zu bytes\n", count);
/* some sanity checks */
err = -EINVAL;
binfmt_misc: expand the register format limit to 1920 bytes The current code places a 256 byte limit on the registration format. This ends up being fairly limited when you try to do matching against a binary format like ELF: - the magic & mask formats cannot have any embedded NUL chars (string_unescape_inplace halts at the first NUL) - each escape sequence quadruples the size: \x00 is needed for NUL - trying to match bytes at the start of the file as well as further on leads to a lot of \x00 sequences in the mask - magic & mask have to be the same length (when decoded) - still need bytes for the other fields - impossible! Let's look at a concrete (and common) example: using QEMU to run MIPS ELFs. The name field uses 11 bytes "qemu-mipsel". The interp uses 20 bytes "/usr/bin/qemu-mipsel". The type & flags takes up 4 bytes. We need 7 bytes for the delimiter (usually ":"). We can skip offset. So already we're down to 107 bytes to use with the magic/mask instead of the real limit of 128 (BINPRM_BUF_SIZE). If people use shell code to register (which they do the majority of the time), they're down to ~26 possible bytes since the escape sequence must be \x##. The ELF format looks like (both 32 & 64 bit): e_ident: 16 bytes e_type: 2 bytes e_machine: 2 bytes Those 20 bytes are enough for most architectures because they have so few formats in the first place, thus they can be uniquely identified. That also means for shell users, since 20 is smaller than 26, they can sanely register a handler. But for some targets (like MIPS), we need to poke further. The ELF fields continue on: e_entry: 4 or 8 bytes e_phoff: 4 or 8 bytes e_shoff: 4 or 8 bytes e_flags: 4 bytes We only care about e_flags here as that includes the bits to identify whether the ELF is O32/N32/N64. But now we have to consume another 16 bytes (for 32 bit ELFs) or 28 bytes (for 64 bit ELFs) just to match the flags. If every byte is escaped, we send 288 more bytes to the kernel ((20 {e_ident,e_type,e_machine} + 12 {e_entry,e_phoff,e_shoff} + 4 {e_flags}) * 2 {mask,magic} * 4 {escape}) and we've clearly blown our budget. Even if we try to be clever and do the decoding ourselves (rather than relying on the kernel to process \x##), we still can't hit the mark -- string_unescape_inplace treats mask & magic as C strings so NUL cannot be embedded. That leaves us with having to pass \x00 for the 12/24 entry/phoff/shoff bytes (as those will be completely random addresses), and that is a minimum requirement of 48/96 bytes for the mask alone. Add up the rest and we blow through it (this is for 64 bit ELFs): magic: 20 {e_ident,e_type,e_machine} + 24 {e_entry,e_phoff,e_shoff} + 4 {e_flags} = 48 # ^^ See note below. mask: 20 {e_ident,e_type,e_machine} + 96 {e_entry,e_phoff,e_shoff} + 4 {e_flags} = 120 Remember above we had 107 left over, and now we're at 168. This is of course the *best* case scenario -- you'll also want to have NUL bytes in the magic & mask too to match literal zeros. Note: the reason we can use 24 in the magic is that we can work off of the fact that for bytes the mask would clobber, we can stuff any value into magic that we want. So when mask is \x00, we don't need the magic to also be \x00, it can be an unescaped raw byte like '!'. This lets us handle more formats (barely) under the current 256 limit, but that's a pretty tall hoop to force people to jump through. With all that said, let's bump the limit from 256 bytes to 1920. This way we support escaping every byte of the mask & magic field (which is 1024 bytes by themselves -- 128 * 4 * 2), and we leave plenty of room for other fields. Like long paths to the interpreter (when you have source in your /really/long/homedir/qemu/foo). Since the current code stuffs more than one structure into the same buffer, we leave a bit of space to easily round up to 2k. 1920 is just as arbitrary as 256 ;). Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-13 22:52:03 +00:00
if ((count < 11) || (count > MAX_REGISTER_LENGTH))
goto out;
err = -ENOMEM;
memsize = sizeof(Node) + count + 8;
e = kmalloc(memsize, GFP_KERNEL);
if (!e)
goto out;
p = buf = (char *)e + sizeof(Node);
memset(e, 0, sizeof(Node));
if (copy_from_user(buf, buffer, count))
goto efault;
del = *p++; /* delimeter */
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: delim: %#x {%c}\n", del, del);
/* Pad the buffer with the delim to simplify parsing below. */
memset(buf + count, del, 8);
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Parse the 'name' field. */
e->name = p;
p = strchr(p, del);
if (!p)
goto einval;
*p++ = '\0';
if (!e->name[0] ||
!strcmp(e->name, ".") ||
!strcmp(e->name, "..") ||
strchr(e->name, '/'))
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: name: {%s}\n", e->name);
/* Parse the 'type' field. */
switch (*p++) {
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
case 'E':
pr_debug("register: type: E (extension)\n");
e->flags = 1 << Enabled;
break;
case 'M':
pr_debug("register: type: M (magic)\n");
e->flags = (1 << Enabled) | (1 << Magic);
break;
default:
goto einval;
}
if (*p++ != del)
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
if (test_bit(Magic, &e->flags)) {
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Handle the 'M' (magic) format. */
char *s;
/* Parse the 'offset' field. */
s = strchr(p, del);
if (!s)
goto einval;
*s++ = '\0';
e->offset = simple_strtoul(p, &p, 10);
if (*p++)
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: offset: %#x\n", e->offset);
/* Parse the 'magic' field. */
e->magic = p;
p = scanarg(p, del);
if (!p)
goto einval;
if (!e->magic[0])
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
if (USE_DEBUG)
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[raw]: ",
DUMP_PREFIX_NONE, e->magic, p - e->magic);
/* Parse the 'mask' field. */
e->mask = p;
p = scanarg(p, del);
if (!p)
goto einval;
if (!e->mask[0]) {
e->mask = NULL;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: mask[raw]: none\n");
} else if (USE_DEBUG)
print_hex_dump_bytes(
KBUILD_MODNAME ": register: mask[raw]: ",
DUMP_PREFIX_NONE, e->mask, p - e->mask);
/*
* Decode the magic & mask fields.
* Note: while we might have accepted embedded NUL bytes from
* above, the unescape helpers here will stop at the first one
* it encounters.
*/
e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
if (e->mask &&
string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
goto einval;
if (e->size + e->offset > BINPRM_BUF_SIZE)
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: magic/mask length: %i\n", e->size);
if (USE_DEBUG) {
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[decoded]: ",
DUMP_PREFIX_NONE, e->magic, e->size);
if (e->mask) {
int i;
char *masked = kmalloc(e->size, GFP_KERNEL);
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
print_hex_dump_bytes(
KBUILD_MODNAME ": register: mask[decoded]: ",
DUMP_PREFIX_NONE, e->mask, e->size);
if (masked) {
for (i = 0; i < e->size; ++i)
masked[i] = e->magic[i] & e->mask[i];
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[masked]: ",
DUMP_PREFIX_NONE, masked, e->size);
kfree(masked);
}
}
}
} else {
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Handle the 'E' (extension) format. */
/* Skip the 'offset' field. */
p = strchr(p, del);
if (!p)
goto einval;
*p++ = '\0';
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Parse the 'magic' field. */
e->magic = p;
p = strchr(p, del);
if (!p)
goto einval;
*p++ = '\0';
if (!e->magic[0] || strchr(e->magic, '/'))
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: extension: {%s}\n", e->magic);
/* Skip the 'mask' field. */
p = strchr(p, del);
if (!p)
goto einval;
*p++ = '\0';
}
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Parse the 'interpreter' field. */
e->interpreter = p;
p = strchr(p, del);
if (!p)
goto einval;
*p++ = '\0';
if (!e->interpreter[0])
goto einval;
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
pr_debug("register: interpreter: {%s}\n", e->interpreter);
binfmt_misc: add comments & debug logs When trying to develop a custom format handler, the errors returned all effectively get bucketed as EINVAL with no kernel messages. The other errors (ENOMEM/EFAULT) are internal/obvious and basic. Thus any time a bad handler is rejected, the developer has to walk the dense code and try to guess where it went wrong. Needing to dive into kernel code is itself a fairly high barrier for a lot of people. To improve this situation, let's deploy extensive pr_debug markers at logical parse points, and add comments to the dense parsing logic. It let's you see exactly where the parsing aborts, the string the kernel received (useful when dealing with shell code), how it translated the buffers to binary data, and how it will apply the mask at runtime. Some example output: $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register $ dmesg binfmt_misc: register: received 92 bytes binfmt_misc: register: delim: 0x3a {:} binfmt_misc: register: name: {qemu-foo} binfmt_misc: register: type: M (magic) binfmt_misc: register: offset: 0x0 binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c \x7fELF\xAD\xAD\ binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00 x01\x00. binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66 \xff\xff\xff\xff binfmt_misc: register: mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30 \xff\x00\xff\x00 binfmt_misc: register: mask[raw]: 00 . binfmt_misc: register: magic/mask length: 8 binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00 .ELF.... binfmt_misc: register: mask[decoded]: ff ff ff ff ff 00 ff 00 ........ binfmt_misc: register: magic[masked]: 7f 45 4c 46 ad 00 01 00 .ELF.... binfmt_misc: register: interpreter: {/usr/bin/qemu-foo} binfmt_misc: register: flag: P (preserve argv0) binfmt_misc: register: flag: O (open binary) binfmt_misc: register: flag: C (preserve creds) The [raw] lines show us exactly what was received from userspace. The lines after that show us how the kernel has decoded things. Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 23:52:08 +00:00
/* Parse the 'flags' field. */
p = check_special_flags(p, e);
if (*p == '\n')
p++;
if (p != buf + count)
goto einval;
return e;
out:
return ERR_PTR(err);
efault:
kfree(e);
return ERR_PTR(-EFAULT);
einval:
kfree(e);
return ERR_PTR(-EINVAL);
}
/*
* Set status of entry/binfmt_misc:
* '1' enables, '0' disables and '-1' clears entry/binfmt_misc
*/
static int parse_command(const char __user *buffer, size_t count)
{
char s[4];
if (count > 3)
return -EINVAL;
if (copy_from_user(s, buffer, count))
return -EFAULT;
if (!count)
return 0;
if (s[count - 1] == '\n')
count--;
if (count == 1 && s[0] == '0')
return 1;
if (count == 1 && s[0] == '1')
return 2;
if (count == 2 && s[0] == '-' && s[1] == '1')
return 3;
return -EINVAL;
}
/* generic stuff */
static void entry_status(Node *e, char *page)
{
char *dp;
char *status = "disabled";
const char *flags = "flags: ";
if (test_bit(Enabled, &e->flags))
status = "enabled";
if (!VERBOSE_STATUS) {
sprintf(page, "%s\n", status);
return;
}
sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
dp = page + strlen(page);
/* print the special flags */
sprintf(dp, "%s", flags);
dp += strlen(flags);
if (e->flags & MISC_FMT_PRESERVE_ARGV0)
*dp++ = 'P';
if (e->flags & MISC_FMT_OPEN_BINARY)
*dp++ = 'O';
if (e->flags & MISC_FMT_CREDENTIALS)
*dp++ = 'C';
*dp++ = '\n';
if (!test_bit(Magic, &e->flags)) {
sprintf(dp, "extension .%s\n", e->magic);
} else {
int i;
sprintf(dp, "offset %i\nmagic ", e->offset);
dp = page + strlen(page);
for (i = 0; i < e->size; i++) {
sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
dp += 2;
}
if (e->mask) {
sprintf(dp, "\nmask ");
dp += 6;
for (i = 0; i < e->size; i++) {
sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
dp += 2;
}
}
*dp++ = '\n';
*dp = '\0';
}
}
static struct inode *bm_get_inode(struct super_block *sb, int mode)
{
struct inode *inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_atime = inode->i_mtime = inode->i_ctime =
current_fs_time(inode->i_sb);
}
return inode;
}
static void bm_evict_inode(struct inode *inode)
{
clear_inode(inode);
kfree(inode->i_private);
}
static void kill_node(Node *e)
{
struct dentry *dentry;
write_lock(&entries_lock);
dentry = e->dentry;
if (dentry) {
list_del_init(&e->list);
e->dentry = NULL;
}
write_unlock(&entries_lock);
if (dentry) {
drop_nlink(dentry->d_inode);
d_drop(dentry);
dput(dentry);
simple_release_fs(&bm_mnt, &entry_count);
}
}
/* /<entry> */
static ssize_t
bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
Node *e = file_inode(file)->i_private;
ssize_t res;
char *page;
page = (char *) __get_free_page(GFP_KERNEL);
if (!page)
return -ENOMEM;
entry_status(e, page);
res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
free_page((unsigned long) page);
return res;
}
static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct dentry *root;
Node *e = file_inode(file)->i_private;
int res = parse_command(buffer, count);
switch (res) {
case 1:
/* Disable this handler. */
clear_bit(Enabled, &e->flags);
break;
case 2:
/* Enable this handler. */
set_bit(Enabled, &e->flags);
break;
case 3:
/* Delete this handler. */
root = dget(file->f_path.dentry->d_sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
kill_node(e);
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
break;
default:
return res;
}
return count;
}
static const struct file_operations bm_entry_operations = {
.read = bm_entry_read,
.write = bm_entry_write,
llseek: automatically add .llseek fop All file_operations should get a .llseek operation so we can make nonseekable_open the default for future file operations without a .llseek pointer. The three cases that we can automatically detect are no_llseek, seq_lseek and default_llseek. For cases where we can we can automatically prove that the file offset is always ignored, we use noop_llseek, which maintains the current behavior of not returning an error from a seek. New drivers should normally not use noop_llseek but instead use no_llseek and call nonseekable_open at open time. Existing drivers can be converted to do the same when the maintainer knows for certain that no user code relies on calling seek on the device file. The generated code is often incorrectly indented and right now contains comments that clarify for each added line why a specific variant was chosen. In the version that gets submitted upstream, the comments will be gone and I will manually fix the indentation, because there does not seem to be a way to do that using coccinelle. Some amount of new code is currently sitting in linux-next that should get the same modifications, which I will do at the end of the merge window. Many thanks to Julia Lawall for helping me learn to write a semantic patch that does all this. ===== begin semantic patch ===== // This adds an llseek= method to all file operations, // as a preparation for making no_llseek the default. // // The rules are // - use no_llseek explicitly if we do nonseekable_open // - use seq_lseek for sequential files // - use default_llseek if we know we access f_pos // - use noop_llseek if we know we don't access f_pos, // but we still want to allow users to call lseek // @ open1 exists @ identifier nested_open; @@ nested_open(...) { <+... nonseekable_open(...) ...+> } @ open exists@ identifier open_f; identifier i, f; identifier open1.nested_open; @@ int open_f(struct inode *i, struct file *f) { <+... ( nonseekable_open(...) | nested_open(...) ) ...+> } @ read disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ read_no_fpos disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { ... when != off } @ write @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ write_no_fpos @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { ... when != off } @ fops0 @ identifier fops; @@ struct file_operations fops = { ... }; @ has_llseek depends on fops0 @ identifier fops0.fops; identifier llseek_f; @@ struct file_operations fops = { ... .llseek = llseek_f, ... }; @ has_read depends on fops0 @ identifier fops0.fops; identifier read_f; @@ struct file_operations fops = { ... .read = read_f, ... }; @ has_write depends on fops0 @ identifier fops0.fops; identifier write_f; @@ struct file_operations fops = { ... .write = write_f, ... }; @ has_open depends on fops0 @ identifier fops0.fops; identifier open_f; @@ struct file_operations fops = { ... .open = open_f, ... }; // use no_llseek if we call nonseekable_open //////////////////////////////////////////// @ nonseekable1 depends on !has_llseek && has_open @ identifier fops0.fops; identifier nso ~= "nonseekable_open"; @@ struct file_operations fops = { ... .open = nso, ... +.llseek = no_llseek, /* nonseekable */ }; @ nonseekable2 depends on !has_llseek @ identifier fops0.fops; identifier open.open_f; @@ struct file_operations fops = { ... .open = open_f, ... +.llseek = no_llseek, /* open uses nonseekable */ }; // use seq_lseek for sequential files ///////////////////////////////////// @ seq depends on !has_llseek @ identifier fops0.fops; identifier sr ~= "seq_read"; @@ struct file_operations fops = { ... .read = sr, ... +.llseek = seq_lseek, /* we have seq_read */ }; // use default_llseek if there is a readdir /////////////////////////////////////////// @ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier readdir_e; @@ // any other fop is used that changes pos struct file_operations fops = { ... .readdir = readdir_e, ... +.llseek = default_llseek, /* readdir is present */ }; // use default_llseek if at least one of read/write touches f_pos ///////////////////////////////////////////////////////////////// @ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read.read_f; @@ // read fops use offset struct file_operations fops = { ... .read = read_f, ... +.llseek = default_llseek, /* read accesses f_pos */ }; @ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, ... + .llseek = default_llseek, /* write accesses f_pos */ }; // Use noop_llseek if neither read nor write accesses f_pos /////////////////////////////////////////////////////////// @ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; identifier write_no_fpos.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, .read = read_f, ... +.llseek = noop_llseek, /* read and write both use no f_pos */ }; @ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write_no_fpos.write_f; @@ struct file_operations fops = { ... .write = write_f, ... +.llseek = noop_llseek, /* write uses no f_pos */ }; @ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; @@ struct file_operations fops = { ... .read = read_f, ... +.llseek = noop_llseek, /* read uses no f_pos */ }; @ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; @@ struct file_operations fops = { ... +.llseek = noop_llseek, /* no read or write fn */ }; ===== End semantic patch ===== Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Julia Lawall <julia@diku.dk> Cc: Christoph Hellwig <hch@infradead.org>
2010-08-15 16:52:59 +00:00
.llseek = default_llseek,
};
/* /register */
static ssize_t bm_register_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
Node *e;
struct inode *inode;
struct dentry *root, *dentry;
struct super_block *sb = file->f_path.dentry->d_sb;
int err = 0;
e = create_entry(buffer, count);
if (IS_ERR(e))
return PTR_ERR(e);
root = dget(sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
dentry = lookup_one_len(e->name, root, strlen(e->name));
err = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out;
err = -EEXIST;
if (dentry->d_inode)
goto out2;
inode = bm_get_inode(sb, S_IFREG | 0644);
err = -ENOMEM;
if (!inode)
goto out2;
err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
if (err) {
iput(inode);
inode = NULL;
goto out2;
}
e->dentry = dget(dentry);
inode->i_private = e;
inode->i_fop = &bm_entry_operations;
d_instantiate(dentry, inode);
write_lock(&entries_lock);
list_add(&e->list, &entries);
write_unlock(&entries_lock);
err = 0;
out2:
dput(dentry);
out:
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
if (err) {
kfree(e);
return -EINVAL;
}
return count;
}
static const struct file_operations bm_register_operations = {
.write = bm_register_write,
llseek: automatically add .llseek fop All file_operations should get a .llseek operation so we can make nonseekable_open the default for future file operations without a .llseek pointer. The three cases that we can automatically detect are no_llseek, seq_lseek and default_llseek. For cases where we can we can automatically prove that the file offset is always ignored, we use noop_llseek, which maintains the current behavior of not returning an error from a seek. New drivers should normally not use noop_llseek but instead use no_llseek and call nonseekable_open at open time. Existing drivers can be converted to do the same when the maintainer knows for certain that no user code relies on calling seek on the device file. The generated code is often incorrectly indented and right now contains comments that clarify for each added line why a specific variant was chosen. In the version that gets submitted upstream, the comments will be gone and I will manually fix the indentation, because there does not seem to be a way to do that using coccinelle. Some amount of new code is currently sitting in linux-next that should get the same modifications, which I will do at the end of the merge window. Many thanks to Julia Lawall for helping me learn to write a semantic patch that does all this. ===== begin semantic patch ===== // This adds an llseek= method to all file operations, // as a preparation for making no_llseek the default. // // The rules are // - use no_llseek explicitly if we do nonseekable_open // - use seq_lseek for sequential files // - use default_llseek if we know we access f_pos // - use noop_llseek if we know we don't access f_pos, // but we still want to allow users to call lseek // @ open1 exists @ identifier nested_open; @@ nested_open(...) { <+... nonseekable_open(...) ...+> } @ open exists@ identifier open_f; identifier i, f; identifier open1.nested_open; @@ int open_f(struct inode *i, struct file *f) { <+... ( nonseekable_open(...) | nested_open(...) ) ...+> } @ read disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ read_no_fpos disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { ... when != off } @ write @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ write_no_fpos @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { ... when != off } @ fops0 @ identifier fops; @@ struct file_operations fops = { ... }; @ has_llseek depends on fops0 @ identifier fops0.fops; identifier llseek_f; @@ struct file_operations fops = { ... .llseek = llseek_f, ... }; @ has_read depends on fops0 @ identifier fops0.fops; identifier read_f; @@ struct file_operations fops = { ... .read = read_f, ... }; @ has_write depends on fops0 @ identifier fops0.fops; identifier write_f; @@ struct file_operations fops = { ... .write = write_f, ... }; @ has_open depends on fops0 @ identifier fops0.fops; identifier open_f; @@ struct file_operations fops = { ... .open = open_f, ... }; // use no_llseek if we call nonseekable_open //////////////////////////////////////////// @ nonseekable1 depends on !has_llseek && has_open @ identifier fops0.fops; identifier nso ~= "nonseekable_open"; @@ struct file_operations fops = { ... .open = nso, ... +.llseek = no_llseek, /* nonseekable */ }; @ nonseekable2 depends on !has_llseek @ identifier fops0.fops; identifier open.open_f; @@ struct file_operations fops = { ... .open = open_f, ... +.llseek = no_llseek, /* open uses nonseekable */ }; // use seq_lseek for sequential files ///////////////////////////////////// @ seq depends on !has_llseek @ identifier fops0.fops; identifier sr ~= "seq_read"; @@ struct file_operations fops = { ... .read = sr, ... +.llseek = seq_lseek, /* we have seq_read */ }; // use default_llseek if there is a readdir /////////////////////////////////////////// @ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier readdir_e; @@ // any other fop is used that changes pos struct file_operations fops = { ... .readdir = readdir_e, ... +.llseek = default_llseek, /* readdir is present */ }; // use default_llseek if at least one of read/write touches f_pos ///////////////////////////////////////////////////////////////// @ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read.read_f; @@ // read fops use offset struct file_operations fops = { ... .read = read_f, ... +.llseek = default_llseek, /* read accesses f_pos */ }; @ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, ... + .llseek = default_llseek, /* write accesses f_pos */ }; // Use noop_llseek if neither read nor write accesses f_pos /////////////////////////////////////////////////////////// @ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; identifier write_no_fpos.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, .read = read_f, ... +.llseek = noop_llseek, /* read and write both use no f_pos */ }; @ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write_no_fpos.write_f; @@ struct file_operations fops = { ... .write = write_f, ... +.llseek = noop_llseek, /* write uses no f_pos */ }; @ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; @@ struct file_operations fops = { ... .read = read_f, ... +.llseek = noop_llseek, /* read uses no f_pos */ }; @ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; @@ struct file_operations fops = { ... +.llseek = noop_llseek, /* no read or write fn */ }; ===== End semantic patch ===== Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Julia Lawall <julia@diku.dk> Cc: Christoph Hellwig <hch@infradead.org>
2010-08-15 16:52:59 +00:00
.llseek = noop_llseek,
};
/* /status */
static ssize_t
bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
char *s = enabled ? "enabled\n" : "disabled\n";
return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
}
static ssize_t bm_status_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
int res = parse_command(buffer, count);
struct dentry *root;
switch (res) {
case 1:
/* Disable all handlers. */
enabled = 0;
break;
case 2:
/* Enable all handlers. */
enabled = 1;
break;
case 3:
/* Delete all handlers. */
root = dget(file->f_path.dentry->d_sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
while (!list_empty(&entries))
kill_node(list_entry(entries.next, Node, list));
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
break;
default:
return res;
}
return count;
}
static const struct file_operations bm_status_operations = {
.read = bm_status_read,
.write = bm_status_write,
llseek: automatically add .llseek fop All file_operations should get a .llseek operation so we can make nonseekable_open the default for future file operations without a .llseek pointer. The three cases that we can automatically detect are no_llseek, seq_lseek and default_llseek. For cases where we can we can automatically prove that the file offset is always ignored, we use noop_llseek, which maintains the current behavior of not returning an error from a seek. New drivers should normally not use noop_llseek but instead use no_llseek and call nonseekable_open at open time. Existing drivers can be converted to do the same when the maintainer knows for certain that no user code relies on calling seek on the device file. The generated code is often incorrectly indented and right now contains comments that clarify for each added line why a specific variant was chosen. In the version that gets submitted upstream, the comments will be gone and I will manually fix the indentation, because there does not seem to be a way to do that using coccinelle. Some amount of new code is currently sitting in linux-next that should get the same modifications, which I will do at the end of the merge window. Many thanks to Julia Lawall for helping me learn to write a semantic patch that does all this. ===== begin semantic patch ===== // This adds an llseek= method to all file operations, // as a preparation for making no_llseek the default. // // The rules are // - use no_llseek explicitly if we do nonseekable_open // - use seq_lseek for sequential files // - use default_llseek if we know we access f_pos // - use noop_llseek if we know we don't access f_pos, // but we still want to allow users to call lseek // @ open1 exists @ identifier nested_open; @@ nested_open(...) { <+... nonseekable_open(...) ...+> } @ open exists@ identifier open_f; identifier i, f; identifier open1.nested_open; @@ int open_f(struct inode *i, struct file *f) { <+... ( nonseekable_open(...) | nested_open(...) ) ...+> } @ read disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ read_no_fpos disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { ... when != off } @ write @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ write_no_fpos @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { ... when != off } @ fops0 @ identifier fops; @@ struct file_operations fops = { ... }; @ has_llseek depends on fops0 @ identifier fops0.fops; identifier llseek_f; @@ struct file_operations fops = { ... .llseek = llseek_f, ... }; @ has_read depends on fops0 @ identifier fops0.fops; identifier read_f; @@ struct file_operations fops = { ... .read = read_f, ... }; @ has_write depends on fops0 @ identifier fops0.fops; identifier write_f; @@ struct file_operations fops = { ... .write = write_f, ... }; @ has_open depends on fops0 @ identifier fops0.fops; identifier open_f; @@ struct file_operations fops = { ... .open = open_f, ... }; // use no_llseek if we call nonseekable_open //////////////////////////////////////////// @ nonseekable1 depends on !has_llseek && has_open @ identifier fops0.fops; identifier nso ~= "nonseekable_open"; @@ struct file_operations fops = { ... .open = nso, ... +.llseek = no_llseek, /* nonseekable */ }; @ nonseekable2 depends on !has_llseek @ identifier fops0.fops; identifier open.open_f; @@ struct file_operations fops = { ... .open = open_f, ... +.llseek = no_llseek, /* open uses nonseekable */ }; // use seq_lseek for sequential files ///////////////////////////////////// @ seq depends on !has_llseek @ identifier fops0.fops; identifier sr ~= "seq_read"; @@ struct file_operations fops = { ... .read = sr, ... +.llseek = seq_lseek, /* we have seq_read */ }; // use default_llseek if there is a readdir /////////////////////////////////////////// @ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier readdir_e; @@ // any other fop is used that changes pos struct file_operations fops = { ... .readdir = readdir_e, ... +.llseek = default_llseek, /* readdir is present */ }; // use default_llseek if at least one of read/write touches f_pos ///////////////////////////////////////////////////////////////// @ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read.read_f; @@ // read fops use offset struct file_operations fops = { ... .read = read_f, ... +.llseek = default_llseek, /* read accesses f_pos */ }; @ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, ... + .llseek = default_llseek, /* write accesses f_pos */ }; // Use noop_llseek if neither read nor write accesses f_pos /////////////////////////////////////////////////////////// @ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; identifier write_no_fpos.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, .read = read_f, ... +.llseek = noop_llseek, /* read and write both use no f_pos */ }; @ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write_no_fpos.write_f; @@ struct file_operations fops = { ... .write = write_f, ... +.llseek = noop_llseek, /* write uses no f_pos */ }; @ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; @@ struct file_operations fops = { ... .read = read_f, ... +.llseek = noop_llseek, /* read uses no f_pos */ }; @ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; @@ struct file_operations fops = { ... +.llseek = noop_llseek, /* no read or write fn */ }; ===== End semantic patch ===== Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Julia Lawall <julia@diku.dk> Cc: Christoph Hellwig <hch@infradead.org>
2010-08-15 16:52:59 +00:00
.llseek = default_llseek,
};
/* Superblock handling */
static const struct super_operations s_ops = {
.statfs = simple_statfs,
.evict_inode = bm_evict_inode,
};
static int bm_fill_super(struct super_block *sb, void *data, int silent)
{
int err;
static struct tree_descr bm_files[] = {
[2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
[3] = {"register", &bm_register_operations, S_IWUSR},
/* last one */ {""}
};
err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
if (!err)
sb->s_op = &s_ops;
return err;
}
static struct dentry *bm_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_single(fs_type, flags, data, bm_fill_super);
}
static struct linux_binfmt misc_format = {
.module = THIS_MODULE,
.load_binary = load_misc_binary,
};
static struct file_system_type bm_fs_type = {
.owner = THIS_MODULE,
.name = "binfmt_misc",
.mount = bm_mount,
.kill_sb = kill_litter_super,
};
fs: Limit sys_mount to only request filesystem modules. Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-03 03:39:14 +00:00
MODULE_ALIAS_FS("binfmt_misc");
static int __init init_misc_binfmt(void)
{
int err = register_filesystem(&bm_fs_type);
if (!err)
insert_binfmt(&misc_format);
return err;
}
static void __exit exit_misc_binfmt(void)
{
unregister_binfmt(&misc_format);
unregister_filesystem(&bm_fs_type);
}
core_initcall(init_misc_binfmt);
module_exit(exit_misc_binfmt);
MODULE_LICENSE("GPL");