Messages in this thread | | | Date | Mon, 19 Nov 2012 08:23:30 -0800 | Subject | Re: yama: lockdep warning on yama_ptracer_del | From | Kees Cook <> |
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On Sun, Nov 18, 2012 at 8:05 PM, Sasha Levin <levinsasha928@gmail.com> wrote: > Hi Kees, > > On Thu, Oct 18, 2012 at 6:39 PM, Kees Cook <keescook@chromium.org> wrote: >> On Wed, Oct 17, 2012 at 8:10 PM, Sasha Levin <sasha.levin@oracle.com> wrote: >>> Hi all, >>> >>> I was fuzzing with trinity within a KVM tools guest (lkvm) on a linux-next kernel, and got the >>> following dump which I believe to be noise due to how the timers work - but I'm not 100% sure. >>> ... >>> [ 954.674123] Possible interrupt unsafe locking scenario: >>> [ 954.674123] >>> [ 954.674123] CPU0 CPU1 >>> [ 954.674123] ---- ---- >>> [ 954.674123] lock(ptracer_relations_lock); >>> [ 954.674123] local_irq_disable(); >>> [ 954.674123] lock(&(&new_timer->it_lock)->rlock); >>> [ 954.674123] lock(ptracer_relations_lock); >>> [ 954.674123] <Interrupt> >>> [ 954.674123] lock(&(&new_timer->it_lock)->rlock); >>> [ 954.674123] >>> [ 954.674123] *** DEADLOCK *** >> >> I've been wanting to get rid of the Yama ptracer_relations_lock >> anyway, so maybe I should do that now just to avoid this case at all? > > I still see this one in -rc6, is there anything to get rid of it > before the release?
I'm not sure about changes to the timer locks, but I haven't been able to get rid of the locking on Yama's task_free path. I did send a patch to get rid of locking during a read, though:
https://lkml.org/lkml/2012/11/13/808
-Kees
-- Kees Cook Chrome OS Security
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