Commit b06075a9 authored Jul 10, 2015 by Mikulas Patocka Committed by Mike Snitzer Jul 13, 2015

dm: fix use after free crash due to incorrect cleanup sequence



Linux 4.2-rc1 Commit 0f20972f ("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: 0f20972f ("dm: factor out a common cleanup_mapped_device()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent 621739b0

drivers/md/dm.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2277,8 +2277,6 @@ static void dm_init_old_md_queue(struct mapped_device *md)

		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 @@ static void cleanup_mapped_device(struct mapped_device *md)
		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;