linux-kernel - Re: [PATCH v2] tty: fix data race in flush_to

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Message-ID: <CAKU3ayVt3Jb3tH8Mq3udM7VpChhN_v1s0-h8E66rdj4u6QcOBg@mail.gmail.com>
Date:	Thu, 17 Sep 2015 09:18:11 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Dmitry Vyukov <dvyukov@...gle.com>, Jiri Slaby <jslaby@...e.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Hans Boehm <hboehm@...gle.com>
Subject: Re: [PATCH v2] tty: fix data race in flush_to_ldisc

On Thu, Sep 17, 2015 at 8:53 AM, Greg KH <gregkh@...uxfoundation.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@...gle.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.

Regards,
Peter Hurley
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