On Thu, 2014-09-11 at 23:52 +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <[email protected]>
> Date: Thu, 11 Sep 2014 23:44:35 +0200
> Subject: futex: Unlock hb->lock in futex_wait_requeue_pi() error path
That's the second time we are bitten by bugs in when requeing, now pi.
We need to reconsider some of our testing tools to stress these paths
better, imo.
> futex_wait_requeue_pi() calls futex_wait_setup(). If
> futex_wait_setup() succeeds it returns with hb->lock held and
> preemption disabled. Now the sanity check after this does:
>
> if (match_futex(&q.key, &key2)) {
> ret = -EINVAL;
> goto out_put_keys;
> }
>
> which releases the keys but does not release hb->lock. So we happily
> return to user space with hb->lock held and therefor preemption
> disabled.
>
> Unlock hb->lock before taking the exit route.
>
> Reported-by: Dave "Trinity" Jones <[email protected]>
> Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]>
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