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dm snapshot: fix crash with transient storage and zero chunk size 

The following commands will crash the kernel:

modprobe brd rd_size=1048576
dmsetup create o --table "0 `blockdev --getsize /dev/ram0` snapshot-origin /dev/ram0"
dmsetup create s --table "0 `blockdev --getsize /dev/ram0` snapshot /dev/ram0 /dev/ram1 N 0"

The reason is that when we test for zero chunk size, we jump to the label
bad_read_metadata without setting the "r" variable. The function
snapshot_ctr destroys all the structures and then exits with "r == 0". The
kernel then crashes because it falsely believes that snapshot_ctr
succeeded.

In order to fix the bug, we set the variable "r" to -EINVAL.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2021-05-10 14:49:05 -04:00 committed by Mike Snitzer
parent 7ee06ddc40
commit c699a0db2d
1 changed files with 1 additions and 0 deletions
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1
drivers/md/dm-snap.c
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@ -1408,6 +1408,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
if (!s->store->chunk_size) {
ti->error = "Chunk size not set";
r = -EINVAL;
goto bad_read_metadata;
}