Re: [PATCH] drm/dp_mst: Check crc4 value while building sideband message

Reviewed-by: Lyude Paul lyude@redhat.com

On Mon, 2020-02-03 at 13:16 +0100, Benjamin Gaignard wrote:

Check that computed crc value is matching the one encoded in the message.

Signed-off-by: Benjamin Gaignard benjamin.gaignard@st.com

CC: lyude@redhat.com CC: airlied@linux.ie CC: jani.nikula@linux.intel.com 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 822d2f177f90..eee899d6742b 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;