fs:Fix Possible deadlock on spinlock "ctx_lock" when user aborts process using async-IO with ctrl-C

This fixes a possible deadlock on spinlock ctx_lock used the percpu ref structure before calling kiocb_cancel, this is due to the issue of us reattempting to lock on calling aio_complete from within kiob_cancel as the kiocb_cancel_fn function pointer which in term causes a deadlock. This is easily fixed by unlocking the ctx_lock with spin_lock_irq and locking afterward the call to kiocb_cancel in order to avoid this deadlock when the user aborts a process using async-IO with ctrl-C.

---
 fs/aio.c | 2 ++
 1 file changed, 2 insertions(+)

index fb8e45b..3107b92 100644
@@ -615,7 +615,9 @@ static void free_ioctx_users(struct percpu_ref *ref)
 				       struct aio_kiocb, ki_list);
 
 		list_del_init(&req->ki_list);
+		spin_unlock_irq(&ctx->ctx_lock);
 		kiocb_cancel(req);
+		spin_lock_irq(&ctx->ctx_lock);
 	}
 
 	spin_unlock_irq(&ctx->ctx_lock);

2.7.4

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