From: Mikulas Patocka mpatocka@redhat.com
commit 7cdf6a0aae1cccf5167f3f04ecddcf648b78e289 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/dm-cache-target.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2193,8 +2193,8 @@ static void wait_for_migrations(struct c
static void stop_worker(struct cache *cache) { - cancel_delayed_work(&cache->waker); - flush_workqueue(cache->wq); + cancel_delayed_work_sync(&cache->waker); + drain_workqueue(cache->wq); }
static void requeue_deferred_cells(struct cache *cache)