From e41f30294b426c6337aa182dc5adc4fea8d2a68a Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Tue, 17 Feb 2015 14:34:00 -0500 Subject: [PATCH] dm snapshot: fix a possible invalid memory access on unload commit 22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3 upstream. 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 Signed-off-by: Ben Hutchings --- drivers/md/dm-snap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index fec79e7fe917..6b94c3ce42ed 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1444,8 +1444,6 @@ out: full_bio->bi_end_io = pe->full_bio_end_io; full_bio->bi_private = pe->full_bio_private; } - free_pending_exception(pe); - increment_pending_exceptions_done_count(); up_write(&s->lock); @@ -1462,6 +1460,8 @@ out: } retry_origin_bios(s, origin_bios); + + free_pending_exception(pe); } static void commit_callback(void *context, int success) -- 2.39.2