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loop: Fix NULL pointer dereference by synchronizing lo_release and loop_queue_rq #816

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loop: Fix NULL pointer dereference by synchronizing lo_release and loop_queue_rq #816

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11 changes: 11 additions & 0 deletions drivers/block/loop.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1118,6 +1118,17 @@ static void __loop_clr_fd(struct loop_device *lo)
struct file *filp;
gfp_t gfp = lo->old_gfp_mask;

/*
* Now that loop_queue_rq() sees lo->lo_state != Lo_bound,
* wait for already started loop_queue_rq() to complete.
*/
synchronize_rcu();
/*
* Now that no more works are scheduled by loop_queue_rq(),
* wait for already scheduled works to complete.
*/
drain_workqueue(lo->workqueue);

spin_lock_irq(&lo->lo_lock);
filp = lo->lo_backing_file;
lo->lo_backing_file = NULL;
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