The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 7cdf6a0aae1cccf5167f3f04ecddcf648b78e289 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka mpatocka@redhat.com Date: Wed, 19 Feb 2020 10:25:45 -0500 Subject: [PATCH] dm cache: fix a crash due to incorrect work item cancelling
The crash can be reproduced by running the lvm2 testsuite test lvconvert-thin-external-cache.sh for several minutes, e.g.: while :; do make check T=shell/lvconvert-thin-external-cache.sh; done
The crash happens in this call chain: do_waker -> policy_tick -> smq_tick -> end_hotspot_period -> clear_bitset -> memset -> __memset -- which accesses an invalid pointer in the vmalloc area.
The work entry on the workqueue is executed even after the bitmap was freed. The problem is that cancel_delayed_work doesn't wait for the running work item to finish, so the work item can continue running and re-submitting itself even after cache_postsuspend. In order to make sure that the work item won't be running, we must use cancel_delayed_work_sync.
Also, change flush_workqueue to drain_workqueue, so that if some work item submits itself or another work item, we are properly waiting for both of them.
Fixes: c6b4fcbad044 ("dm: add cache target") Cc: stable@vger.kernel.org # v3.9 Signed-off-by: Mikulas Patocka mpatocka@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 2d32821b3a5b..f4be63671233 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2846,8 +2846,8 @@ static void cache_postsuspend(struct dm_target *ti) prevent_background_work(cache); BUG_ON(atomic_read(&cache->nr_io_migrations));
- cancel_delayed_work(&cache->waker); - flush_workqueue(cache->wq); + cancel_delayed_work_sync(&cache->waker); + drain_workqueue(cache->wq); WARN_ON(cache->tracker.in_flight);
/*