linux-stable/fs/adfs/super.c
Eric W. Biederman 7f78e03513 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 19:36:31 -08:00

552 lines
13 KiB
C

/*
* linux/fs/adfs/super.c
*
* Copyright (C) 1997-1999 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/buffer_head.h>
#include <linux/parser.h>
#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/statfs.h>
#include <linux/user_namespace.h>
#include "adfs.h"
#include "dir_f.h"
#include "dir_fplus.h"
#define ADFS_DEFAULT_OWNER_MASK S_IRWXU
#define ADFS_DEFAULT_OTHER_MASK (S_IRWXG | S_IRWXO)
void __adfs_error(struct super_block *sb, const char *function, const char *fmt, ...)
{
char error_buf[128];
va_list args;
va_start(args, fmt);
vsnprintf(error_buf, sizeof(error_buf), fmt, args);
va_end(args);
printk(KERN_CRIT "ADFS-fs error (device %s)%s%s: %s\n",
sb->s_id, function ? ": " : "",
function ? function : "", error_buf);
}
static int adfs_checkdiscrecord(struct adfs_discrecord *dr)
{
int i;
/* sector size must be 256, 512 or 1024 bytes */
if (dr->log2secsize != 8 &&
dr->log2secsize != 9 &&
dr->log2secsize != 10)
return 1;
/* idlen must be at least log2secsize + 3 */
if (dr->idlen < dr->log2secsize + 3)
return 1;
/* we cannot have such a large disc that we
* are unable to represent sector offsets in
* 32 bits. This works out at 2.0 TB.
*/
if (le32_to_cpu(dr->disc_size_high) >> dr->log2secsize)
return 1;
/* idlen must be no greater than 19 v2 [1.0] */
if (dr->idlen > 19)
return 1;
/* reserved bytes should be zero */
for (i = 0; i < sizeof(dr->unused52); i++)
if (dr->unused52[i] != 0)
return 1;
return 0;
}
static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map)
{
unsigned int v0, v1, v2, v3;
int i;
v0 = v1 = v2 = v3 = 0;
for (i = sb->s_blocksize - 4; i; i -= 4) {
v0 += map[i] + (v3 >> 8);
v3 &= 0xff;
v1 += map[i + 1] + (v0 >> 8);
v0 &= 0xff;
v2 += map[i + 2] + (v1 >> 8);
v1 &= 0xff;
v3 += map[i + 3] + (v2 >> 8);
v2 &= 0xff;
}
v0 += v3 >> 8;
v1 += map[1] + (v0 >> 8);
v2 += map[2] + (v1 >> 8);
v3 += map[3] + (v2 >> 8);
return v0 ^ v1 ^ v2 ^ v3;
}
static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm)
{
unsigned char crosscheck = 0, zonecheck = 1;
int i;
for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
unsigned char *map;
map = dm[i].dm_bh->b_data;
if (adfs_calczonecheck(sb, map) != map[0]) {
adfs_error(sb, "zone %d fails zonecheck", i);
zonecheck = 0;
}
crosscheck ^= map[3];
}
if (crosscheck != 0xff)
adfs_error(sb, "crosscheck != 0xff");
return crosscheck == 0xff && zonecheck;
}
static void adfs_put_super(struct super_block *sb)
{
int i;
struct adfs_sb_info *asb = ADFS_SB(sb);
for (i = 0; i < asb->s_map_size; i++)
brelse(asb->s_map[i].dm_bh);
kfree(asb->s_map);
kfree(asb);
sb->s_fs_info = NULL;
}
static int adfs_show_options(struct seq_file *seq, struct dentry *root)
{
struct adfs_sb_info *asb = ADFS_SB(root->d_sb);
if (!uid_eq(asb->s_uid, GLOBAL_ROOT_UID))
seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, asb->s_uid));
if (!gid_eq(asb->s_gid, GLOBAL_ROOT_GID))
seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, asb->s_gid));
if (asb->s_owner_mask != ADFS_DEFAULT_OWNER_MASK)
seq_printf(seq, ",ownmask=%o", asb->s_owner_mask);
if (asb->s_other_mask != ADFS_DEFAULT_OTHER_MASK)
seq_printf(seq, ",othmask=%o", asb->s_other_mask);
if (asb->s_ftsuffix != 0)
seq_printf(seq, ",ftsuffix=%u", asb->s_ftsuffix);
return 0;
}
enum {Opt_uid, Opt_gid, Opt_ownmask, Opt_othmask, Opt_ftsuffix, Opt_err};
static const match_table_t tokens = {
{Opt_uid, "uid=%u"},
{Opt_gid, "gid=%u"},
{Opt_ownmask, "ownmask=%o"},
{Opt_othmask, "othmask=%o"},
{Opt_ftsuffix, "ftsuffix=%u"},
{Opt_err, NULL}
};
static int parse_options(struct super_block *sb, char *options)
{
char *p;
struct adfs_sb_info *asb = ADFS_SB(sb);
int option;
if (!options)
return 0;
while ((p = strsep(&options, ",")) != NULL) {
substring_t args[MAX_OPT_ARGS];
int token;
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case Opt_uid:
if (match_int(args, &option))
return -EINVAL;
asb->s_uid = make_kuid(current_user_ns(), option);
if (!uid_valid(asb->s_uid))
return -EINVAL;
break;
case Opt_gid:
if (match_int(args, &option))
return -EINVAL;
asb->s_gid = make_kgid(current_user_ns(), option);
if (!gid_valid(asb->s_gid))
return -EINVAL;
break;
case Opt_ownmask:
if (match_octal(args, &option))
return -EINVAL;
asb->s_owner_mask = option;
break;
case Opt_othmask:
if (match_octal(args, &option))
return -EINVAL;
asb->s_other_mask = option;
break;
case Opt_ftsuffix:
if (match_int(args, &option))
return -EINVAL;
asb->s_ftsuffix = option;
break;
default:
printk("ADFS-fs: unrecognised mount option \"%s\" "
"or missing value\n", p);
return -EINVAL;
}
}
return 0;
}
static int adfs_remount(struct super_block *sb, int *flags, char *data)
{
*flags |= MS_NODIRATIME;
return parse_options(sb, data);
}
static int adfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *sb = dentry->d_sb;
struct adfs_sb_info *sbi = ADFS_SB(sb);
u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
buf->f_type = ADFS_SUPER_MAGIC;
buf->f_namelen = sbi->s_namelen;
buf->f_bsize = sb->s_blocksize;
buf->f_blocks = sbi->s_size;
buf->f_files = sbi->s_ids_per_zone * sbi->s_map_size;
buf->f_bavail =
buf->f_bfree = adfs_map_free(sb);
buf->f_ffree = (long)(buf->f_bfree * buf->f_files) / (long)buf->f_blocks;
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
return 0;
}
static struct kmem_cache *adfs_inode_cachep;
static struct inode *adfs_alloc_inode(struct super_block *sb)
{
struct adfs_inode_info *ei;
ei = (struct adfs_inode_info *)kmem_cache_alloc(adfs_inode_cachep, GFP_KERNEL);
if (!ei)
return NULL;
return &ei->vfs_inode;
}
static void adfs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(adfs_inode_cachep, ADFS_I(inode));
}
static void adfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, adfs_i_callback);
}
static void init_once(void *foo)
{
struct adfs_inode_info *ei = (struct adfs_inode_info *) foo;
inode_init_once(&ei->vfs_inode);
}
static int init_inodecache(void)
{
adfs_inode_cachep = kmem_cache_create("adfs_inode_cache",
sizeof(struct adfs_inode_info),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD),
init_once);
if (adfs_inode_cachep == NULL)
return -ENOMEM;
return 0;
}
static void destroy_inodecache(void)
{
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(adfs_inode_cachep);
}
static const struct super_operations adfs_sops = {
.alloc_inode = adfs_alloc_inode,
.destroy_inode = adfs_destroy_inode,
.write_inode = adfs_write_inode,
.put_super = adfs_put_super,
.statfs = adfs_statfs,
.remount_fs = adfs_remount,
.show_options = adfs_show_options,
};
static struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr)
{
struct adfs_discmap *dm;
unsigned int map_addr, zone_size, nzones;
int i, zone;
struct adfs_sb_info *asb = ADFS_SB(sb);
nzones = asb->s_map_size;
zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
map_addr = (nzones >> 1) * zone_size -
((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
map_addr = signed_asl(map_addr, asb->s_map2blk);
asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);
dm = kmalloc(nzones * sizeof(*dm), GFP_KERNEL);
if (dm == NULL) {
adfs_error(sb, "not enough memory");
return NULL;
}
for (zone = 0; zone < nzones; zone++, map_addr++) {
dm[zone].dm_startbit = 0;
dm[zone].dm_endbit = zone_size;
dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
dm[zone].dm_bh = sb_bread(sb, map_addr);
if (!dm[zone].dm_bh) {
adfs_error(sb, "unable to read map");
goto error_free;
}
}
/* adjust the limits for the first and last map zones */
i = zone - 1;
dm[0].dm_startblk = 0;
dm[0].dm_startbit = ADFS_DR_SIZE_BITS;
dm[i].dm_endbit = (le32_to_cpu(dr->disc_size_high) << (32 - dr->log2bpmb)) +
(le32_to_cpu(dr->disc_size) >> dr->log2bpmb) +
(ADFS_DR_SIZE_BITS - i * zone_size);
if (adfs_checkmap(sb, dm))
return dm;
adfs_error(sb, "map corrupted");
error_free:
while (--zone >= 0)
brelse(dm[zone].dm_bh);
kfree(dm);
return NULL;
}
static inline unsigned long adfs_discsize(struct adfs_discrecord *dr, int block_bits)
{
unsigned long discsize;
discsize = le32_to_cpu(dr->disc_size_high) << (32 - block_bits);
discsize |= le32_to_cpu(dr->disc_size) >> block_bits;
return discsize;
}
static int adfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct adfs_discrecord *dr;
struct buffer_head *bh;
struct object_info root_obj;
unsigned char *b_data;
struct adfs_sb_info *asb;
struct inode *root;
sb->s_flags |= MS_NODIRATIME;
asb = kzalloc(sizeof(*asb), GFP_KERNEL);
if (!asb)
return -ENOMEM;
sb->s_fs_info = asb;
/* set default options */
asb->s_uid = GLOBAL_ROOT_UID;
asb->s_gid = GLOBAL_ROOT_GID;
asb->s_owner_mask = ADFS_DEFAULT_OWNER_MASK;
asb->s_other_mask = ADFS_DEFAULT_OTHER_MASK;
asb->s_ftsuffix = 0;
if (parse_options(sb, data))
goto error;
sb_set_blocksize(sb, BLOCK_SIZE);
if (!(bh = sb_bread(sb, ADFS_DISCRECORD / BLOCK_SIZE))) {
adfs_error(sb, "unable to read superblock");
goto error;
}
b_data = bh->b_data + (ADFS_DISCRECORD % BLOCK_SIZE);
if (adfs_checkbblk(b_data)) {
if (!silent)
printk("VFS: Can't find an adfs filesystem on dev "
"%s.\n", sb->s_id);
goto error_free_bh;
}
dr = (struct adfs_discrecord *)(b_data + ADFS_DR_OFFSET);
/*
* Do some sanity checks on the ADFS disc record
*/
if (adfs_checkdiscrecord(dr)) {
if (!silent)
printk("VPS: Can't find an adfs filesystem on dev "
"%s.\n", sb->s_id);
goto error_free_bh;
}
brelse(bh);
if (sb_set_blocksize(sb, 1 << dr->log2secsize)) {
bh = sb_bread(sb, ADFS_DISCRECORD / sb->s_blocksize);
if (!bh) {
adfs_error(sb, "couldn't read superblock on "
"2nd try.");
goto error;
}
b_data = bh->b_data + (ADFS_DISCRECORD % sb->s_blocksize);
if (adfs_checkbblk(b_data)) {
adfs_error(sb, "disc record mismatch, very weird!");
goto error_free_bh;
}
dr = (struct adfs_discrecord *)(b_data + ADFS_DR_OFFSET);
} else {
if (!silent)
printk(KERN_ERR "VFS: Unsupported blocksize on dev "
"%s.\n", sb->s_id);
goto error;
}
/*
* blocksize on this device should now be set to the ADFS log2secsize
*/
sb->s_magic = ADFS_SUPER_MAGIC;
asb->s_idlen = dr->idlen;
asb->s_map_size = dr->nzones | (dr->nzones_high << 8);
asb->s_map2blk = dr->log2bpmb - dr->log2secsize;
asb->s_size = adfs_discsize(dr, sb->s_blocksize_bits);
asb->s_version = dr->format_version;
asb->s_log2sharesize = dr->log2sharesize;
asb->s_map = adfs_read_map(sb, dr);
if (!asb->s_map)
goto error_free_bh;
brelse(bh);
/*
* set up enough so that we can read an inode
*/
sb->s_op = &adfs_sops;
dr = (struct adfs_discrecord *)(asb->s_map[0].dm_bh->b_data + 4);
root_obj.parent_id = root_obj.file_id = le32_to_cpu(dr->root);
root_obj.name_len = 0;
/* Set root object date as 01 Jan 1987 00:00:00 */
root_obj.loadaddr = 0xfff0003f;
root_obj.execaddr = 0xec22c000;
root_obj.size = ADFS_NEWDIR_SIZE;
root_obj.attr = ADFS_NDA_DIRECTORY | ADFS_NDA_OWNER_READ |
ADFS_NDA_OWNER_WRITE | ADFS_NDA_PUBLIC_READ;
root_obj.filetype = -1;
/*
* If this is a F+ disk with variable length directories,
* get the root_size from the disc record.
*/
if (asb->s_version) {
root_obj.size = le32_to_cpu(dr->root_size);
asb->s_dir = &adfs_fplus_dir_ops;
asb->s_namelen = ADFS_FPLUS_NAME_LEN;
} else {
asb->s_dir = &adfs_f_dir_ops;
asb->s_namelen = ADFS_F_NAME_LEN;
}
/*
* ,xyz hex filetype suffix may be added by driver
* to files that have valid RISC OS filetype
*/
if (asb->s_ftsuffix)
asb->s_namelen += 4;
sb->s_d_op = &adfs_dentry_operations;
root = adfs_iget(sb, &root_obj);
sb->s_root = d_make_root(root);
if (!sb->s_root) {
int i;
for (i = 0; i < asb->s_map_size; i++)
brelse(asb->s_map[i].dm_bh);
kfree(asb->s_map);
adfs_error(sb, "get root inode failed\n");
goto error;
}
return 0;
error_free_bh:
brelse(bh);
error:
sb->s_fs_info = NULL;
kfree(asb);
return -EINVAL;
}
static struct dentry *adfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, adfs_fill_super);
}
static struct file_system_type adfs_fs_type = {
.owner = THIS_MODULE,
.name = "adfs",
.mount = adfs_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("adfs");
static int __init init_adfs_fs(void)
{
int err = init_inodecache();
if (err)
goto out1;
err = register_filesystem(&adfs_fs_type);
if (err)
goto out;
return 0;
out:
destroy_inodecache();
out1:
return err;
}
static void __exit exit_adfs_fs(void)
{
unregister_filesystem(&adfs_fs_type);
destroy_inodecache();
}
module_init(init_adfs_fs)
module_exit(exit_adfs_fs)
MODULE_LICENSE("GPL");