From: Mikulas Patocka Date: Tue, 17 Feb 2015 19:34:00 +0000 (-0500) Subject: dm snapshot: fix a possible invalid memory access on unload X-Git-Tag: firefly_0821_release~176^2~2249^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3;p=firefly-linux-kernel-4.4.55.git dm snapshot: fix a possible invalid memory access on unload When the snapshot target is unloaded, snapshot_dtr() waits until pending_exceptions_count drops to zero. Then, it destroys the snapshot. Therefore, the function that decrements pending_exceptions_count should not touch the snapshot structure after the decrement. pending_complete() calls free_pending_exception(), which decrements pending_exceptions_count, and then it performs up_write(&s->lock) and it calls retry_origin_bios() which dereferences s->origin. These two memory accesses to the fields of the snapshot may touch the dm_snapshot struture after it is freed. This patch moves the call to free_pending_exception() to the end of pending_complete(), so that the snapshot will not be destroyed while pending_complete() is in progress. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 864b03f47727..8b204ae216ab 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1432,8 +1432,6 @@ out: full_bio->bi_private = pe->full_bio_private; atomic_inc(&full_bio->bi_remaining); } - free_pending_exception(pe); - increment_pending_exceptions_done_count(); up_write(&s->lock); @@ -1450,6 +1448,8 @@ out: } retry_origin_bios(s, origin_bios); + + free_pending_exception(pe); } static void commit_callback(void *context, int success)