| 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: dm cache: fix a crash due to incorrect work item cancelling |
| |
| 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 |
| @@ -2846,8 +2846,8 @@ static void cache_postsuspend(struct dm_ |
| 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); |
| |
| /* |
