Re: [PATCH 3.16 083/254] dmaengine: dmatest: move callback wait queue to thread context

[Ben Hutchings]

On Wed, 2018-02-28 at 12:47 -0500, Adam Wallis wrote:
> Ben
> 
> 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.
> > 
> > ------------------
> > 
> > From: Adam Wallis <awallis@xxxxxxxxxxxxxx>
> > 
> > commit 6f6a23a213be51728502b88741ba6a10cda2441d upstream.
> > 
> > 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).
> > 
> > Commit a9df21e34b42 ("dmaengine: dmatest: warn user when dma test times
> > out") attempted to WARN the user that the stack was likely corrupted but
> > did not fix the actual issue.
> > 
> > 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.
> > 
> > Bug: https://bugzilla.kernel.org/show_bug.cgi?id=197605
> > Fixes: adfa543e7314 ("dmatest: don't use set_freezable_with_signal()")
> > Reviewed-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> > Suggested-by: Shunyong Yang <shunyong.yang@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Adam Wallis <awallis@xxxxxxxxxxxxxx>
> > Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
> > Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> 
> [..]
> 
> Make sure you pick up the following bug fix on whatever branch you apply the
> above patch to
> 
> 
> From 66b3bd2356e0a1531c71a3dcf96944621e25c17c Mon Sep 17 00:00:00 2001
> From: Yang Shunyong <shunyong.yang@xxxxxxxxxxxxxxxx>
> Date: Mon, 29 Jan 2018 14:40:11 +0800
> Subject: dmaengine: dmatest: fix container_of member in dmatest_callback
> 
> From: Yang Shunyong <shunyong.yang@xxxxxxxxxxxxxxxx>
> 
> 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.
> 
> Fixes: 6f6a23a213be ("dmaengine: dmatest: move callback wait ...")
> Signed-off-by: Yang Shunyong <shunyong.yang@xxxxxxxxxxxxxxxx>
> Acked-by: Adam Wallis <awallis@xxxxxxxxxxxxxx>
> Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> 
> 
-- 
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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