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Message-ID: <1520091209.2617.372.camel@decadent.org.uk>
Subject: Re: [PATCH 3.16 083/254] dmaengine: dmatest: move callback wait
 queue to thread context
From:   Ben Hutchings <ben@decadent.org.uk>
To:     Adam Wallis <awallis@codeaurora.org>, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Cc:     akpm@linux-foundation.org, Sinan Kaya <okaya@codeaurora.org>,
        Vinod Koul <vinod.koul@intel.com>,
        Shunyong Yang <shunyong.yang@hxt-semitech.com>
Date:   Sat, 03 Mar 2018 15:33:29 +0000
In-Reply-To: <ff67c838-e4e4-c254-1a6d-4b395e63604b@codeaurora.org>
References: <lsq.1519831218.227690932@decadent.org.uk>
         <ff67c838-e4e4-c254-1a6d-4b395e63604b@codeaurora.org>
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On Wed, 2018-02-28 at 12:47 -0500, Adam Wallis wrote:
> Ben
>=20
> On 2/28/2018 10:20 AM, Ben Hutchings wrote:
> > 3.16.55-rc1 review patch.  If anyone has any objections, please let me =
know.
> >=20
> > ------------------
> >=20
> > From: Adam Wallis <awallis@codeaurora.org>
> >=20
> > commit 6f6a23a213be51728502b88741ba6a10cda2441d upstream.
> >=20
> > Commit adfa543e7314 ("dmatest: don't use set_freezable_with_signal()")
> > introduced a bug (that is in fact documented by the patch commit text)
> > that leaves behind a dangling pointer. Since the done_wait structure is
> > allocated on the stack, future invocations to the DMATEST can produce
> > undesirable results (e.g., corrupted spinlocks).
> >=20
> > Commit a9df21e34b42 ("dmaengine: dmatest: warn user when dma test times
> > out") attempted to WARN the user that the stack was likely corrupted bu=
t
> > did not fix the actual issue.
> >=20
> > This patch fixes the issue by pushing the wait queue and callback
> > structs into the the thread structure. If a failure occurs due to time,
> > dmaengine_terminate_all will force the callback to safely call
> > wake_up_all() without possibility of using a freed pointer.
> >=20
> > Bug: https://bugzilla.kernel.org/show_bug.cgi?id=3D197605
> > Fixes: adfa543e7314 ("dmatest: don't use set_freezable_with_signal()")
> > Reviewed-by: Sinan Kaya <okaya@codeaurora.org>
> > Suggested-by: Shunyong Yang <shunyong.yang@hxt-semitech.com>
> > Signed-off-by: Adam Wallis <awallis@codeaurora.org>
> > Signed-off-by: Vinod Koul <vinod.koul@intel.com>
> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
>=20
> [..]
>=20
> Make sure you pick up the following bug fix on whatever branch you apply =
the
> above patch to
>=20
>=20
> From 66b3bd2356e0a1531c71a3dcf96944621e25c17c Mon Sep 17 00:00:00 2001
> From: Yang Shunyong <shunyong.yang@hxt-semitech.com>
> Date: Mon, 29 Jan 2018 14:40:11 +0800
> Subject: dmaengine: dmatest: fix container_of member in dmatest_callback
>=20
> From: Yang Shunyong <shunyong.yang@hxt-semitech.com>
>=20
> commit 66b3bd2356e0a1531c71a3dcf96944621e25c17c upstream.

Thanks, I've added this.

Ben.

> The type of arg passed to dmatest_callback is struct dmatest_done.
> It refers to test_done in struct dmatest_thread, not done_wait.
>=20
> Fixes: 6f6a23a213be ("dmaengine: dmatest: move callback wait ...")
> Signed-off-by: Yang Shunyong <shunyong.yang@hxt-semitech.com>
> Acked-by: Adam Wallis <awallis@codeaurora.org>
> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>=20
>=20
>=20
--=20
Ben Hutchings
[W]e found...that it wasn't as easy to get programs right as we had
thought.
... I realized that a large part of my life from then on was going to
be spent
in finding mistakes in my own programs. - Maurice Wilkes, 1949


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