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dm ioctl: Avoid pointer arithmetic overflow

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Especially on 32-bit systems, it is possible for the pointer
arithmetic to overflow and cause a userspace pointer to be
dereferenced in the kernel.

Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Demi Marie Obenour 2023-06-03 10:52:40 -04:00 committed by Mike Snitzer
parent b60528d9e6
commit 13f4a697f8
1 changed files with 16 additions and 0 deletions
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16
drivers/md/dm-ioctl.c
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@ -1397,6 +1397,22 @@ static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
static_assert(__alignof__(struct dm_target_spec) <= 8,
"struct dm_target_spec must not require more than 8-byte alignment");
/*
* Number of bytes remaining, starting with last. This is always
* sizeof(struct dm_target_spec) or more, as otherwise *last was
* out of bounds already.
*/
size_t remaining = (char *)end - (char *)last;
/*
* There must be room for both the next target spec and the
* NUL-terminator of the target itself.
*/
if (remaining - sizeof(struct dm_target_spec) <= next) {
DMERR("Target spec extends beyond end of parameters");
return -EINVAL;
}
if (next % __alignof__(struct dm_target_spec)) {
DMERR("Next dm_target_spec (offset %u) is not %zu-byte aligned",
next, __alignof__(struct dm_target_spec));