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

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Linux 4.2-rc1 Commit 0f20972f7b ("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: 0f20972f7b ("dm: factor out a common cleanup_mapped_device()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2015-07-10 17:21:43 -04:00 committed by Mike Snitzer
parent 621739b00e
commit b06075a98d
1 changed files with 2 additions and 2 deletions
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4
drivers/md/dm.c
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@ -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;