linux-kernel - Re: [PATCH v5 1/3] tty: fix data race in flush_to

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Message-ID: <CAKU3ayVKt0VR3R5-T4zncNbv+-HQ93yqVhDXp2mCxQZL4OD2_A@mail.gmail.com>
Date:	Thu, 17 Sep 2015 13:37:53 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	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 v5 1/3] tty: fix data race in flush_to_ldisc

On Thu, Sep 17, 2015 at 11:17 AM, Dmitry Vyukov <dvyukov@...gle.com> 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).

Reviewed-by: Peter Hurley <peter@...leysoftware.com>
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