linux-kernel - [PATCH v1 RFC] video/hdmi: Fix HDMI_VENDOR_INFOFRAME

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Date:   Mon,  9 Jan 2023 23:31:10 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Helge Deller <deller@....de>, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Hans Verkuil <hans.verkuil@...co.com>,
        ville.syrjala@...ux.intel.com,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Bernard Zhao <bernard@...o.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH v1 RFC] video/hdmi: Fix HDMI_VENDOR_INFOFRAME_SIZE

When support for the HDMI vendor infoframe was introduced back with
commit 7d27becb3532 ("video/hdmi: Introduce helpers for the HDMI vendor
specific infoframe") it's payload size was either 5 or 6 bytes,
depending on:
  if (frame->s3d_struct >= HDMI_3D_STRUCTURE_SIDE_BY_SIDE_HALF)
When true the size was 6 bytes, otherwise 5 bytes.

Drivers that are using hdmi_infoframe_pack() are reserving 10 bytes (4
bytes for the header and up to 6 bytes for the infoframe payload data)
or more (exynos_hdmi reserves 25 bytes).

Over time the frame payload length was reduced to 4 bytes. This however
does not match the code from hdmi_hdmi_infoframe_pack() where ptr[8] and
ptr[9] are written, which means the infoframe has to allow up to 6 bytes
of payload data (considering that the header takes 4 bytes).

Change HDMI_VENDOR_INFOFRAME_SIZE to 6 bytes so
hdmi_vendor_infoframe_pack_only() can properly check the passed buffer
size and avoid an out of bounds write to ptr[8] or ptr[9].

Fixes: c5e69ab35c0d ("video/hdmi: Constify infoframe passed to the pack functions")
Fixes: d43be2554b58 ("drivers: video: hdmi: cleanup coding style in video a bit")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
I'm not an expert on this topic and I'm not sure if the size still
depends on that if condition from long time ago. So please share your
thoughts.

 include/linux/hdmi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index 2f4dcc8d060e..026c5ef5a1a5 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -57,7 +57,7 @@ enum hdmi_infoframe_type {
 #define HDMI_SPD_INFOFRAME_SIZE    25
 #define HDMI_AUDIO_INFOFRAME_SIZE  10
 #define HDMI_DRM_INFOFRAME_SIZE    26
-#define HDMI_VENDOR_INFOFRAME_SIZE  4
+#define HDMI_VENDOR_INFOFRAME_SIZE  6

 #define HDMI_INFOFRAME_SIZE(type)	\
 	(HDMI_INFOFRAME_HEADER_SIZE + HDMI_ ## type ## _INFOFRAME_SIZE)
-- 
2.39.0