From f82c1c596a29d42c9835bc3aa4ee4b41ff735da8 Mon Sep 17 00:00:00 2001
From: Benjamin Gaignard <benjamin.gaignard@st.com>
Date: Mon, 3 Feb 2020 13:16:20 +0100
Subject: drm/dp_mst: Check crc4 value while building sideband message
Git-commit: d6b8bbca6bc83b9c57e528b28df6177b9b57e19d
Patch-mainline: v5.7-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
Check that computed crc value is matching the one encoded in the message.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200203121620.9002-1-benjamin.gaignard@st.com
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 93af73406a49..a0a77066e3b9 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -736,6 +736,10 @@ static bool drm_dp_sideband_msg_build(struct drm_dp_sideband_msg_rx *msg,
if (msg->curchunk_idx >= msg->curchunk_len) {
/* do CRC */
crc4 = drm_dp_msg_data_crc4(msg->chunk, msg->curchunk_len - 1);
+ if (crc4 != msg->chunk[msg->curchunk_len - 1])
+ print_hex_dump(KERN_DEBUG, "wrong crc",
+ DUMP_PREFIX_NONE, 16, 1,
+ msg->chunk, msg->curchunk_len, false);
/* copy chunk into bigger msg */
memcpy(&msg->msg[msg->curlen], msg->chunk, msg->curchunk_len - 1);
msg->curlen += msg->curchunk_len - 1;
--
2.28.0