drm/amd: Sanity check the ACPI EDID

An HP Pavilion Aero Laptop 13-be0xxx/8916 has an ACPI EDID, but using
it is causing corruption. It's got illogical values of not specifying
a digital interface. Sanity check the ACPI EDID to avoid tripping such
problems.

Suggested-by: Tobias Jakobi <[email protected]>
Reported-and-tested-by: Chris Bainbridge <[email protected]>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3782
Fixes: c6a8370 ("drm/amd/display: Fetch the EDID from _DDC if available for eDP")
Reviewed-by: Harry Wentland <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: superm1

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c

@@ -907,14 +907,14 @@ dm_helpers_probe_acpi_edid(void *data, u8 *buf, unsigned int block, size_t len)
 	struct drm_connector *connector = data;
 	struct acpi_device *acpidev = ACPI_COMPANION(connector->dev->dev);
 	unsigned char start = block * EDID_LENGTH;
-	void *edid;
+	struct edid *edid;
 	int r;
 
 	if (!acpidev)
 		return -ENODEV;
 
 	/* fetch the entire edid from BIOS */
-	r = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, &edid);
+	r = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, (void *)&edid);
 	if (r < 0) {
 		drm_dbg(connector->dev, "Failed to get EDID from ACPI: %d\n", r);
 		return r;
@@ -924,7 +924,14 @@ dm_helpers_probe_acpi_edid(void *data, u8 *buf, unsigned int block, size_t len)
 		goto cleanup;
 	}
 
-	memcpy(buf, edid + start, len);
+	/* sanity check */
+	if (edid->revision < 4 || !(edid->input & DRM_EDID_INPUT_DIGITAL) ||
+	    (edid->input & DRM_EDID_DIGITAL_TYPE_MASK) == DRM_EDID_DIGITAL_TYPE_UNDEF) {
+		r = -EINVAL;
+		goto cleanup;
+	}
+
+	memcpy(buf, (void *)edid + start, len);
 	r = 0;
 
 cleanup: