Re: timerfd: use-after-free in timerfd_remove_cancel

From	Dmitry Vyukov <dvyukov@google.com>
Newsgroups	linux.kernel
Subject	Re: timerfd: use-after-free in timerfd_remove_cancel
Date	2017-01-31 13:20 +0100
Message-ID	<t5FzH-AF-7@gated-at.bofh.it> (permalink)
References	<t5pbz-7p2-9@gated-at.bofh.it> <t5EX1-8E-27@gated-at.bofh.it> <t5F6G-bX-23@gated-at.bofh.it>
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On Tue, Jan 31, 2017 at 12:45 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 31 Jan 2017, Thomas Gleixner wrote:
>
>> On Mon, 30 Jan 2017, Dmitry Vyukov wrote:
>> >
>> > Seems that ctx->might_cancel is racy.
>>
>> Yes, it is. Fix below.
>
> And the fix is racy as well. Darn, we really need to lock the context to
> avoid that mess.

Yes. I think we need to lock most of timerfd_settime. Otherwise we can
end up with a timer that needs to be in the cancel list, but it is
actually not; or vice versa.

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timerfd: use-after-free in timerfd_remove_cancel Dmitry Vyukov <dvyukov@google.com> - 2017-01-30 19:50 +0100
  Re: timerfd: use-after-free in timerfd_remove_cancel Mateusz Guzik <mguzik@redhat.com> - 2017-01-31 03:10 +0100
    Re: timerfd: use-after-free in timerfd_remove_cancel Dmitry Vyukov <dvyukov@google.com> - 2017-01-31 09:30 +0100
  Re: timerfd: use-after-free in timerfd_remove_cancel Thomas Gleixner <tglx@linutronix.de> - 2017-01-31 12:40 +0100
    Re: timerfd: use-after-free in timerfd_remove_cancel Thomas Gleixner <tglx@linutronix.de> - 2017-01-31 12:50 +0100
      Re: timerfd: use-after-free in timerfd_remove_cancel Dmitry Vyukov <dvyukov@google.com> - 2017-01-31 13:20 +0100

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