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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans Verkuil <hans.verkuil@cisco.com>,
        Lyude Paul <lyude@redhat.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Lee Jones <lee.jones@linaro.org>
Subject: [PATCH 4.19 54/54] drm_dp_mst_topology: fix broken drm_dp_sideband_parse_remote_dpcd_read()
Date:   Sat, 11 Apr 2020 14:09:36 +0200
Message-Id: <20200411115513.995604050@linuxfoundation.org>
In-Reply-To: <20200411115508.284500414@linuxfoundation.org>
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From: Hans Verkuil <hans.verkuil@cisco.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@cisco.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e72ddac2-1dc0-100a-d816-9ac98ac009dd@xs4all.nl
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -439,6 +439,7 @@ 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;