From 6a7fb7dd1b1da7e49e030a0638c4371abcff1fe8 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 30 Jun 2021 21:03:57 +0800 Subject: [PATCH] dm snapshot: fix crash with transient storage and zero chunk size stable inclusion from linux-4.19.192 commit 1ff004c41c8205d7677f7b9d7da238a5d9a29274 -------------------------------- commit c699a0db2d62e3bbb7f0bf35c87edbc8d23e3062 upstream. 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 Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang --- drivers/md/dm-snap.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 9e930a150aa2..7d9683629471 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1286,6 +1286,7 @@ 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; } -- GitLab