On Mon, Jul 22, 2019 at 02:38:34PM +0000, Simon Ser wrote:
> From: Simon Ser <simon.ser@xxxxxxxxx>
>
> The VSDB parsing code contains a few len >= N checks, accessing db[N] on
> success. However if len == N, db[N] is out-of-bounds.
>
> This commit changes the checks to test for len > N.
I'm not familiar with this at all, but is db[0] the header and db[1] to db[len]
the data block? In that case, it's not out of bounds.
I looked up the spec and it says:
Length of following data block (in bytes) (02h)
Sean
>
> Signed-off-by: Simon Ser <contact@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_edid.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 82a4ceed3fcf..13d632f14172 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3569,7 +3569,7 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len,
> vic_len = db[8 + offset] >> 5;
> hdmi_3d_len = db[8 + offset] & 0x1f;
>
> - for (i = 0; i < vic_len && len >= (9 + offset + i); i++) {
> + for (i = 0; i < vic_len && len > (9 + offset + i); i++) {
> u8 vic;
>
> vic = db[9 + offset + i];
> @@ -3971,11 +3971,11 @@ drm_parse_hdr_metadata_block(struct drm_connector *connector, const u8 *db)
> connector->hdr_sink_metadata.hdmi_type1.metadata_type =
> hdr_metadata_type(db);
>
> - if (len >= 4)
> + if (len > 4)
> connector->hdr_sink_metadata.hdmi_type1.max_cll = db[4];
> - if (len >= 5)
> + if (len > 5)
> connector->hdr_sink_metadata.hdmi_type1.max_fall = db[5];
> - if (len >= 6)
> + if (len > 6)
> connector->hdr_sink_metadata.hdmi_type1.min_cll = db[6];
> }
>
> @@ -3984,19 +3984,19 @@ drm_parse_hdmi_vsdb_audio(struct drm_connector *connector, const u8 *db)
> {
> u8 len = cea_db_payload_len(db);
>
> - if (len >= 6 && (db[6] & (1 << 7)))
> + if (len > 6 && (db[6] & (1 << 7)))
> connector->eld[DRM_ELD_SAD_COUNT_CONN_TYPE] |= DRM_ELD_SUPPORTS_AI;
> - if (len >= 8) {
> + if (len > 8) {
> connector->latency_present[0] = db[8] >> 7;
> connector->latency_present[1] = (db[8] >> 6) & 1;
> }
> - if (len >= 9)
> + if (len > 9)
> connector->video_latency[0] = db[9];
> - if (len >= 10)
> + if (len > 10)
> connector->audio_latency[0] = db[10];
> - if (len >= 11)
> + if (len > 11)
> connector->video_latency[1] = db[11];
> - if (len >= 12)
> + if (len > 12)
> connector->audio_latency[1] = db[12];
>
> DRM_DEBUG_KMS("HDMI: latency present %d %d, "
> @@ -4559,9 +4559,9 @@ drm_parse_hdmi_vsdb_video(struct drm_connector *connector, const u8 *db)
> struct drm_display_info *info = &connector->display_info;
> u8 len = cea_db_payload_len(db);
>
> - if (len >= 6)
> + if (len > 6)
> info->dvi_dual = db[6] & 1;
> - if (len >= 7)
> + if (len > 7)
> info->max_tmds_clock = db[7] * 5000;
>
> DRM_DEBUG_KMS("HDMI: DVI dual %d, "
> --
> 2.22.0
>
>
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--
Sean Paul, Software Engineer, Google / Chromium OS
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