linux-kernel - [PATCH 4.4 29/29] drm_dp_mst_topology: fix broken drm_dp_sideband_parse_remote_dpcd

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Message-Id: <20200411115412.719714953@linuxfoundation.org>
Date:   Sat, 11 Apr 2020 14:08:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>,
        Lyude Paul <lyude@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Lee Jones <lee.jones@...aro.org>
Subject: [PATCH 4.4 29/29] drm_dp_mst_topology: fix broken drm_dp_sideband_parse_remote_dpcd_read()

From: Hans Verkuil <hans.verkuil@...co.com>

commit a4c30a4861c54af78c4eb8b7855524c1a96d9f80 upstream.

When parsing the reply of a DP_REMOTE_DPCD_READ DPCD command the
result is wrong due to a missing idx increment.

This was never noticed since DP_REMOTE_DPCD_READ is currently not
used, but if you enable it, then it is all wrong.

Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
Reviewed-by: Lyude Paul <lyude@...hat.com>
Acked-by: Alex Deucher <alexander.deucher@....com>
Link: https://patchwork.freedesktop.org/patch/msgid/e72ddac2-1dc0-100a-d816-9ac98ac009dd@xs4all.nl
Signed-off-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -431,6 +431,7 @@ static bool drm_dp_sideband_parse_remote
 	if (idx > raw->curlen)
 		goto fail_len;
 	repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
+	idx++;
 	if (idx > raw->curlen)
 		goto fail_len;