linux-stable/fs/remap_range.c
David Sterba b7a9a503c3 fs: use UB-safe check for signed addition overflow in remap_verify_area
The following warning pops up with enabled UBSAN in tests fstests/generic/303:

  [23127.529395] UBSAN: Undefined behaviour in fs/read_write.c:1725:7
  [23127.529400] signed integer overflow:
  [23127.529403] 4611686018427322368 + 9223372036854775807 cannot be represented in type 'long long int'
  [23127.529412] CPU: 4 PID: 26180 Comm: xfs_io Not tainted 5.2.0-rc2-1.ge195904-vanilla+ #450
  [23127.556999] Hardware name: empty empty/S3993, BIOS PAQEX0-3 02/24/2008
  [23127.557001] Call Trace:
  [23127.557060]  dump_stack+0x67/0x9b
  [23127.557070]  ubsan_epilogue+0x9/0x40
  [23127.573496]  handle_overflow+0xb3/0xc0
  [23127.573514]  do_clone_file_range+0x28f/0x2a0
  [23127.573547]  vfs_clone_file_range+0x35/0xb0
  [23127.573564]  ioctl_file_clone+0x8d/0xc0
  [23127.590144]  do_vfs_ioctl+0x300/0x700
  [23127.590160]  ksys_ioctl+0x70/0x80
  [23127.590203]  ? trace_hardirqs_off_thunk+0x1a/0x1c
  [23127.590210]  __x64_sys_ioctl+0x16/0x20
  [23127.590215]  do_syscall_64+0x5c/0x1d0
  [23127.590224]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  [23127.590231] RIP: 0033:0x7ff6d7250327
  [23127.590241] RSP: 002b:00007ffe3a38f1d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
  [23127.590246] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007ff6d7250327
  [23127.590249] RDX: 00007ffe3a38f220 RSI: 000000004020940d RDI: 0000000000000003
  [23127.590252] RBP: 0000000000000000 R08: 00007ffe3a3c80a0 R09: 00007ffe3a3c8080
  [23127.590255] R10: 000000000fa99fa0 R11: 0000000000000206 R12: 0000000000000000
  [23127.590260] R13: 0000000000000000 R14: 3fffffffffff0000 R15: 00007ff6d750a20c

As loff_t is a signed type, we should use the safe overflow checks
instead of relying on compiler implementation.

The bogus values are intentional and the test is supposed to verify the
boundary conditions.

Signed-off-by: David Sterba <dsterba@suse.com>
Message-Id: <20230523162628.17071-1-dsterba@suse.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-05-24 11:03:59 +02:00

572 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/sched/xacct.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include <linux/dax.h>
#include <linux/overflow.h>
#include "internal.h"
#include <linux/uaccess.h>
#include <asm/unistd.h>
/*
* Performs necessary checks before doing a clone.
*
* Can adjust amount of bytes to clone via @req_count argument.
* Returns appropriate error code that caller should return or
* zero in case the clone should be allowed.
*/
static int generic_remap_checks(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t *req_count, unsigned int remap_flags)
{
struct inode *inode_in = file_in->f_mapping->host;
struct inode *inode_out = file_out->f_mapping->host;
uint64_t count = *req_count;
uint64_t bcount;
loff_t size_in, size_out;
loff_t bs = inode_out->i_sb->s_blocksize;
int ret;
/* The start of both ranges must be aligned to an fs block. */
if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_out, bs))
return -EINVAL;
/* Ensure offsets don't wrap. */
if (pos_in + count < pos_in || pos_out + count < pos_out)
return -EINVAL;
size_in = i_size_read(inode_in);
size_out = i_size_read(inode_out);
/* Dedupe requires both ranges to be within EOF. */
if ((remap_flags & REMAP_FILE_DEDUP) &&
(pos_in >= size_in || pos_in + count > size_in ||
pos_out >= size_out || pos_out + count > size_out))
return -EINVAL;
/* Ensure the infile range is within the infile. */
if (pos_in >= size_in)
return -EINVAL;
count = min(count, size_in - (uint64_t)pos_in);
ret = generic_write_check_limits(file_out, pos_out, &count);
if (ret)
return ret;
/*
* If the user wanted us to link to the infile's EOF, round up to the
* next block boundary for this check.
*
* Otherwise, make sure the count is also block-aligned, having
* already confirmed the starting offsets' block alignment.
*/
if (pos_in + count == size_in &&
(!(remap_flags & REMAP_FILE_DEDUP) || pos_out + count == size_out)) {
bcount = ALIGN(size_in, bs) - pos_in;
} else {
if (!IS_ALIGNED(count, bs))
count = ALIGN_DOWN(count, bs);
bcount = count;
}
/* Don't allow overlapped cloning within the same file. */
if (inode_in == inode_out &&
pos_out + bcount > pos_in &&
pos_out < pos_in + bcount)
return -EINVAL;
/*
* We shortened the request but the caller can't deal with that, so
* bounce the request back to userspace.
*/
if (*req_count != count && !(remap_flags & REMAP_FILE_CAN_SHORTEN))
return -EINVAL;
*req_count = count;
return 0;
}
static int remap_verify_area(struct file *file, loff_t pos, loff_t len,
bool write)
{
loff_t tmp;
if (unlikely(pos < 0 || len < 0))
return -EINVAL;
if (unlikely(check_add_overflow(pos, len, &tmp)))
return -EINVAL;
return security_file_permission(file, write ? MAY_WRITE : MAY_READ);
}
/*
* Ensure that we don't remap a partial EOF block in the middle of something
* else. Assume that the offsets have already been checked for block
* alignment.
*
* For clone we only link a partial EOF block above or at the destination file's
* EOF. For deduplication we accept a partial EOF block only if it ends at the
* destination file's EOF (can not link it into the middle of a file).
*
* Shorten the request if possible.
*/
static int generic_remap_check_len(struct inode *inode_in,
struct inode *inode_out,
loff_t pos_out,
loff_t *len,
unsigned int remap_flags)
{
u64 blkmask = i_blocksize(inode_in) - 1;
loff_t new_len = *len;
if ((*len & blkmask) == 0)
return 0;
if (pos_out + *len < i_size_read(inode_out))
new_len &= ~blkmask;
if (new_len == *len)
return 0;
if (remap_flags & REMAP_FILE_CAN_SHORTEN) {
*len = new_len;
return 0;
}
return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL;
}
/* Read a page's worth of file data into the page cache. */
static struct folio *vfs_dedupe_get_folio(struct file *file, loff_t pos)
{
return read_mapping_folio(file->f_mapping, pos >> PAGE_SHIFT, file);
}
/*
* Lock two folios, ensuring that we lock in offset order if the folios
* are from the same file.
*/
static void vfs_lock_two_folios(struct folio *folio1, struct folio *folio2)
{
/* Always lock in order of increasing index. */
if (folio1->index > folio2->index)
swap(folio1, folio2);
folio_lock(folio1);
if (folio1 != folio2)
folio_lock(folio2);
}
/* Unlock two folios, being careful not to unlock the same folio twice. */
static void vfs_unlock_two_folios(struct folio *folio1, struct folio *folio2)
{
folio_unlock(folio1);
if (folio1 != folio2)
folio_unlock(folio2);
}
/*
* Compare extents of two files to see if they are the same.
* Caller must have locked both inodes to prevent write races.
*/
static int vfs_dedupe_file_range_compare(struct file *src, loff_t srcoff,
struct file *dest, loff_t dstoff,
loff_t len, bool *is_same)
{
bool same = true;
int error = -EINVAL;
while (len) {
struct folio *src_folio, *dst_folio;
void *src_addr, *dst_addr;
loff_t cmp_len = min(PAGE_SIZE - offset_in_page(srcoff),
PAGE_SIZE - offset_in_page(dstoff));
cmp_len = min(cmp_len, len);
if (cmp_len <= 0)
goto out_error;
src_folio = vfs_dedupe_get_folio(src, srcoff);
if (IS_ERR(src_folio)) {
error = PTR_ERR(src_folio);
goto out_error;
}
dst_folio = vfs_dedupe_get_folio(dest, dstoff);
if (IS_ERR(dst_folio)) {
error = PTR_ERR(dst_folio);
folio_put(src_folio);
goto out_error;
}
vfs_lock_two_folios(src_folio, dst_folio);
/*
* Now that we've locked both folios, make sure they're still
* mapped to the file data we're interested in. If not,
* someone is invalidating pages on us and we lose.
*/
if (!folio_test_uptodate(src_folio) || !folio_test_uptodate(dst_folio) ||
src_folio->mapping != src->f_mapping ||
dst_folio->mapping != dest->f_mapping) {
same = false;
goto unlock;
}
src_addr = kmap_local_folio(src_folio,
offset_in_folio(src_folio, srcoff));
dst_addr = kmap_local_folio(dst_folio,
offset_in_folio(dst_folio, dstoff));
flush_dcache_folio(src_folio);
flush_dcache_folio(dst_folio);
if (memcmp(src_addr, dst_addr, cmp_len))
same = false;
kunmap_local(dst_addr);
kunmap_local(src_addr);
unlock:
vfs_unlock_two_folios(src_folio, dst_folio);
folio_put(dst_folio);
folio_put(src_folio);
if (!same)
break;
srcoff += cmp_len;
dstoff += cmp_len;
len -= cmp_len;
}
*is_same = same;
return 0;
out_error:
return error;
}
/*
* Check that the two inodes are eligible for cloning, the ranges make
* sense, and then flush all dirty data. Caller must ensure that the
* inodes have been locked against any other modifications.
*
* If there's an error, then the usual negative error code is returned.
* Otherwise returns 0 with *len set to the request length.
*/
int
__generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t *len, unsigned int remap_flags,
const struct iomap_ops *dax_read_ops)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);
bool same_inode = (inode_in == inode_out);
int ret;
/* Don't touch certain kinds of inodes */
if (IS_IMMUTABLE(inode_out))
return -EPERM;
if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
return -ETXTBSY;
/* Don't reflink dirs, pipes, sockets... */
if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
return -EISDIR;
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
return -EINVAL;
/* Zero length dedupe exits immediately; reflink goes to EOF. */
if (*len == 0) {
loff_t isize = i_size_read(inode_in);
if ((remap_flags & REMAP_FILE_DEDUP) || pos_in == isize)
return 0;
if (pos_in > isize)
return -EINVAL;
*len = isize - pos_in;
if (*len == 0)
return 0;
}
/* Check that we don't violate system file offset limits. */
ret = generic_remap_checks(file_in, pos_in, file_out, pos_out, len,
remap_flags);
if (ret || *len == 0)
return ret;
/* Wait for the completion of any pending IOs on both files */
inode_dio_wait(inode_in);
if (!same_inode)
inode_dio_wait(inode_out);
ret = filemap_write_and_wait_range(inode_in->i_mapping,
pos_in, pos_in + *len - 1);
if (ret)
return ret;
ret = filemap_write_and_wait_range(inode_out->i_mapping,
pos_out, pos_out + *len - 1);
if (ret)
return ret;
/*
* Check that the extents are the same.
*/
if (remap_flags & REMAP_FILE_DEDUP) {
bool is_same = false;
if (!IS_DAX(inode_in))
ret = vfs_dedupe_file_range_compare(file_in, pos_in,
file_out, pos_out, *len, &is_same);
else if (dax_read_ops)
ret = dax_dedupe_file_range_compare(inode_in, pos_in,
inode_out, pos_out, *len, &is_same,
dax_read_ops);
else
return -EINVAL;
if (ret)
return ret;
if (!is_same)
return -EBADE;
}
ret = generic_remap_check_len(inode_in, inode_out, pos_out, len,
remap_flags);
if (ret || *len == 0)
return ret;
/* If can't alter the file contents, we're done. */
if (!(remap_flags & REMAP_FILE_DEDUP))
ret = file_modified(file_out);
return ret;
}
int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t *len, unsigned int remap_flags)
{
return __generic_remap_file_range_prep(file_in, pos_in, file_out,
pos_out, len, remap_flags, NULL);
}
EXPORT_SYMBOL(generic_remap_file_range_prep);
loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags)
{
loff_t ret;
WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);
if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
return -EXDEV;
ret = generic_file_rw_checks(file_in, file_out);
if (ret < 0)
return ret;
if (!file_in->f_op->remap_file_range)
return -EOPNOTSUPP;
ret = remap_verify_area(file_in, pos_in, len, false);
if (ret)
return ret;
ret = remap_verify_area(file_out, pos_out, len, true);
if (ret)
return ret;
ret = file_in->f_op->remap_file_range(file_in, pos_in,
file_out, pos_out, len, remap_flags);
if (ret < 0)
return ret;
fsnotify_access(file_in);
fsnotify_modify(file_out);
return ret;
}
EXPORT_SYMBOL(do_clone_file_range);
loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags)
{
loff_t ret;
file_start_write(file_out);
ret = do_clone_file_range(file_in, pos_in, file_out, pos_out, len,
remap_flags);
file_end_write(file_out);
return ret;
}
EXPORT_SYMBOL(vfs_clone_file_range);
/* Check whether we are allowed to dedupe the destination file */
static bool allow_file_dedupe(struct file *file)
{
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);
if (capable(CAP_SYS_ADMIN))
return true;
if (file->f_mode & FMODE_WRITE)
return true;
if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
return true;
if (!inode_permission(idmap, inode, MAY_WRITE))
return true;
return false;
}
loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
struct file *dst_file, loff_t dst_pos,
loff_t len, unsigned int remap_flags)
{
loff_t ret;
WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP |
REMAP_FILE_CAN_SHORTEN));
ret = mnt_want_write_file(dst_file);
if (ret)
return ret;
/*
* This is redundant if called from vfs_dedupe_file_range(), but other
* callers need it and it's not performance sesitive...
*/
ret = remap_verify_area(src_file, src_pos, len, false);
if (ret)
goto out_drop_write;
ret = remap_verify_area(dst_file, dst_pos, len, true);
if (ret)
goto out_drop_write;
ret = -EPERM;
if (!allow_file_dedupe(dst_file))
goto out_drop_write;
ret = -EXDEV;
if (file_inode(src_file)->i_sb != file_inode(dst_file)->i_sb)
goto out_drop_write;
ret = -EISDIR;
if (S_ISDIR(file_inode(dst_file)->i_mode))
goto out_drop_write;
ret = -EINVAL;
if (!dst_file->f_op->remap_file_range)
goto out_drop_write;
if (len == 0) {
ret = 0;
goto out_drop_write;
}
ret = dst_file->f_op->remap_file_range(src_file, src_pos, dst_file,
dst_pos, len, remap_flags | REMAP_FILE_DEDUP);
out_drop_write:
mnt_drop_write_file(dst_file);
return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range_one);
int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
{
struct file_dedupe_range_info *info;
struct inode *src = file_inode(file);
u64 off;
u64 len;
int i;
int ret;
u16 count = same->dest_count;
loff_t deduped;
if (!(file->f_mode & FMODE_READ))
return -EINVAL;
if (same->reserved1 || same->reserved2)
return -EINVAL;
off = same->src_offset;
len = same->src_length;
if (S_ISDIR(src->i_mode))
return -EISDIR;
if (!S_ISREG(src->i_mode))
return -EINVAL;
if (!file->f_op->remap_file_range)
return -EOPNOTSUPP;
ret = remap_verify_area(file, off, len, false);
if (ret < 0)
return ret;
ret = 0;
if (off + len > i_size_read(src))
return -EINVAL;
/* Arbitrary 1G limit on a single dedupe request, can be raised. */
len = min_t(u64, len, 1 << 30);
/* pre-format output fields to sane values */
for (i = 0; i < count; i++) {
same->info[i].bytes_deduped = 0ULL;
same->info[i].status = FILE_DEDUPE_RANGE_SAME;
}
for (i = 0, info = same->info; i < count; i++, info++) {
struct fd dst_fd = fdget(info->dest_fd);
struct file *dst_file = dst_fd.file;
if (!dst_file) {
info->status = -EBADF;
goto next_loop;
}
if (info->reserved) {
info->status = -EINVAL;
goto next_fdput;
}
deduped = vfs_dedupe_file_range_one(file, off, dst_file,
info->dest_offset, len,
REMAP_FILE_CAN_SHORTEN);
if (deduped == -EBADE)
info->status = FILE_DEDUPE_RANGE_DIFFERS;
else if (deduped < 0)
info->status = deduped;
else
info->bytes_deduped = len;
next_fdput:
fdput(dst_fd);
next_loop:
if (fatal_signal_pending(current))
break;
}
return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range);