btrfs: async-thread: Fix a use-after-free error for trace

Parameter of trace_btrfs_work_queued() can be freed in its workqueue.
So no one use use that pointer after queue_work().

Fix the user-after-free bug by move the trace line before queue_work().

Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 88d9af3..5fb60ea 100644 (file)
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -328,8 +328,8 @@ static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq,
                list_add_tail(&work->ordered_list, &wq->ordered_list);
                spin_unlock_irqrestore(&wq->list_lock, flags);
        }
-       queue_work(wq->normal_wq, &work->normal_work);
        trace_btrfs_work_queued(work);
+       queue_work(wq->normal_wq, &work->normal_work);
 }
 
 void btrfs_queue_work(struct btrfs_workqueue *wq,