linux-kernel - Re: [PATCH v3 2/2] drm/bridge: ti-sn65dsi86: Never store more than msg->size bytes in AUX xfer

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Message-ID: <CAD=FV=U8eJ3J_zY2uaCYGcEjuxkNeTUd1ir33r1f0Xdk+nD3sQ@mail.gmail.com>
Date: Mon, 18 Dec 2023 08:48:00 -0800
From: Doug Anderson <dianders@...omium.org>
To: dri-devel@...ts.freedesktop.org
Cc: Guenter Roeck <groeck@...omium.org>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Jonas Karlman <jonas@...boo.se>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Sam Ravnborg <sam@...nborg.org>, Stephen Boyd <swboyd@...omium.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] drm/bridge: ti-sn65dsi86: Never store more than
 msg->size bytes in AUX xfer

Hi,

On Thu, Dec 14, 2023 at 12:38 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> For aux reads, the value `msg->size` indicates the size of the buffer
> provided by `msg->buffer`. We should never in any circumstances write
> more bytes to the buffer since it may overflow the buffer.
>
> In the ti-sn65dsi86 driver there is one code path that reads the
> transfer length from hardware. Even though it's never been seen to be
> a problem, we should make extra sure that the hardware isn't
> increasing the length since doing so would cause us to overrun the
> buffer.
>
> Fixes: 982f589bde7a ("drm/bridge: ti-sn65dsi86: Update reply on aux failures")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
> (no changes since v2)
>
> Changes in v2:
> - Updated patch subject to match ps8640 patch.
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Since the patch fixes a potential crash, has two Reviews (even if
they're both from @chromium), and doesn't seem controversial, I didn't
want a full week and just landed it in drm-misc-fixes. If anyone is
upset by this then please shout and we can revert or I can post a
followup patch.

Pushed to drm-misc-fixes:

aca58eac52b8 drm/bridge: ti-sn65dsi86: Never store more than msg->size
bytes in AUX xfer