Re: [PATCH] media: v4l2-core: fix VIDIOC_DQEVENT handling on non-x86

[John Stultz]

On Mon, Oct 25, 2021 at 10:50 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> 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@xxxxxxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

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

Thanks so much again Arnd!
-john