dm: fix use after free crash due to incorrect cleanup sequence
Linux 4.2-rc1 Commit 0f20972f7bf6 ("dm: factor out a common
cleanup_mapped_device()") moved a common cleanup code to a separate
function. Unfortunately, that commit incorrectly changed the order of
cleanup, so that it destroys the mapped_device's srcu structure
'io_barrier' before destroying its workqueue.
The function that is executed on the workqueue (dm_wq_work) uses the srcu
structure, thus it may use it after being freed. That results in a
crash in the LVM test suite's mirror-vgreduce-removemissing.sh test.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 0f20972f7bf6 ("dm: factor out a common cleanup_mapped_device()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index de70377..ab37ae1 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2277,8 +2277,6 @@
static void cleanup_mapped_device(struct mapped_device *md)
{
- cleanup_srcu_struct(&md->io_barrier);
-
if (md->wq)
destroy_workqueue(md->wq);
if (md->kworker_task)
@@ -2290,6 +2288,8 @@
if (md->bs)
bioset_free(md->bs);
+ cleanup_srcu_struct(&md->io_barrier);
+
if (md->disk) {
spin_lock(&_minor_lock);
md->disk->private_data = NULL;