linux-kernel - Re: [PATCH] media: v4l2-core: fix VIDIOC

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Date:   Mon, 25 Oct 2021 22:54:23 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Arnd Bergmann <arnd@...db.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-media <linux-media@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: v4l2-core: fix VIDIOC_DQEVENT handling on non-x86

On Mon, Oct 25, 2021 at 10:50 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> My previous bugfix addressed an API inconsistency found by syzbot,
> and it correctly fixed the issue on x86-64 machines, which now behave
> correctly for both native and compat tasks.
>
> Unfortunately, John found that the patch broke compat mode on all other
> architectures, as they can no longer rely on the VIDIOC_DQEVENT_TIME32
> code from the native handler as a fallback in the compat code.
>
> The best way I can see for addressing this is to generalize the
> VIDIOC_DQEVENT32_TIME32 code from x86 and use that for all architectures,
> leaving only the VIDIOC_DQEVENT32 variant as x86 specific. The original
> code was trying to be clever and use the same conversion helper for native
> 32-bit code and compat mode, but that turned out to be too obscure so
> even I missed that bit I had introduced myself when I made the fix.
>
> Fixes: c344f07aa1b4 ("media: v4l2-core: ignore native time32 ioctls on 64-bit")
> Reported-by: John Stultz <john.stultz@...aro.org>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Tested-by: John Stultz <john.stultz@...aro.org>

Thanks so much again Arnd!
-john