Re: [PATCH v2] tty: fix data race in flush_to_ldisc

From	Greg KH <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] tty: fix data race in flush_to_ldisc
Date	2015-09-17 16:00 +0200
Message-ID	<q9HTc-5nL-9@gated-at.bofh.it> (permalink)
References	<q9ELD-TQ-11@gated-at.bofh.it> <q9GXa-40N-37@gated-at.bofh.it> <q9Hgt-4Dp-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Sep 17, 2015 at 09:18:11AM -0400, Peter Hurley wrote:
> On Thu, Sep 17, 2015 at 8:53 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Thu, Sep 17, 2015 at 12:39:36PM +0200, Dmitry Vyukov wrote:
> >> flush_to_ldisc reads port->itty and checks that it is not NULL,
> >> concurrently release_tty sets port->itty to NULL. It is possible
> >> that flush_to_ldisc loads port->itty once, ensures that it is
> >> not NULL, but then reloads it again and uses. The second load
> >> can already return NULL, which will cause a crash.
> >>
> >> Use READ_ONCE to read port->itty.
> >>
> >> The data race was found with KernelThreadSanitizer (KTSAN).
> >>
> >> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> >
> > You sent 3 patches here, but no hint as to what order they need to be
> > applied in.  Please resend them as a patch series (i.e. 1/3, 2/3, 3/3)
> > so they can be applied correctly.
> 
> Greg,
> 
> I don't think these 3 patches are dependent on each other; I think they
> can be applied in any order.

How do I know that?  :)
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[PATCH v2] tty: fix data race in flush_to_ldisc Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 12:40 +0200
  Re: [PATCH v2] tty: fix data race in flush_to_ldisc Greg KH <gregkh@linuxfoundation.org> - 2015-09-17 15:00 +0200
    Re: [PATCH v2] tty: fix data race in flush_to_ldisc Peter Hurley <peter@hurleysoftware.com> - 2015-09-17 15:20 +0200
      Re: [PATCH v2] tty: fix data race in flush_to_ldisc Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 15:30 +0200
        Re: [PATCH v2] tty: fix data race in flush_to_ldisc Greg KH <gregkh@linuxfoundation.org> - 2015-09-17 16:00 +0200
      Re: [PATCH v2] tty: fix data race in flush_to_ldisc Greg KH <gregkh@linuxfoundation.org> - 2015-09-17 16:00 +0200

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