drm: edid: Add bounds checking to HDMI VSDB parsing

The length of HDMI VSDB must be at least 5 bytes. Other than the minimum,
nothing else about the length is specified. Check the length before
accessing any additional field beyond the minimum length.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 21 insertions, 12 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7f392534abcc..eadaf4800f46 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1576,19 +1576,28 @@ add_cea_modes(struct drm_connector *connector, struct edid *edid)
 }
 
 static void
-parse_hdmi_vsdb(struct drm_connector *connector, uint8_t *db)
+parse_hdmi_vsdb(struct drm_connector *connector, const u8 *db)
 {
-        connector->eld[5] |= (db[6] >> 7) << 1;  /* Supports_AI */
+        u8 len = cea_db_payload_len(db);
 
-        connector->dvi_dual = db[6] & 1;
-        connector->max_tmds_clock = db[7] * 5;
-
-        connector->latency_present[0] = db[8] >> 7;
-        connector->latency_present[1] = (db[8] >> 6) & 1;
-        connector->video_latency[0] = db[9];
-        connector->audio_latency[0] = db[10];
-        connector->video_latency[1] = db[11];
-        connector->audio_latency[1] = db[12];
+        if (len >= 6) {
+                connector->eld[5] |= (db[6] >> 7) << 1;  /* Supports_AI */
+                connector->dvi_dual = db[6] & 1;
+        }
+        if (len >= 7)
+                connector->max_tmds_clock = db[7] * 5;
+        if (len >= 8) {
+                connector->latency_present[0] = db[8] >> 7;
+                connector->latency_present[1] = (db[8] >> 6) & 1;
+        }
+        if (len >= 9)
+                connector->video_latency[0] = db[9];
+        if (len >= 10)
+                connector->audio_latency[0] = db[10];
+        if (len >= 11)
+                connector->video_latency[1] = db[11];
+        if (len >= 12)
+                connector->audio_latency[1] = db[12];
 
         DRM_LOG_KMS("HDMI: DVI dual %d, "
                     "max TMDS clock %d, "
@@ -1684,7 +1693,7 @@ void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
                                 break;
                         case VENDOR_BLOCK:
                                 /* HDMI Vendor-Specific Data Block */
-                                if (db[1] == 0x03 && db[2] == 0x0c && db[3] == 0)
+                                if (dbl >= 5 && db[1] == 0x03 && db[2] == 0x0c && db[3] == 0)
                                         parse_hdmi_vsdb(connector, db);
                                 break;
                         default: