On Thu, 11 Sep 2014, Davidlohr Bueso wrote:
> 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.
Testing tools are nice. What we really need is more competent eyes
looking at that code ...
> > 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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