[PATCH] drm/edid: fix invalid EDID extension block filtering

[Jani Nikula]

The invalid EDID block filtering uses the number of valid EDID
extensions instead of all EDID extensions for looping the extensions in
the copy. This is fine, by coincidence, if all the invalid blocks are at
the end of the EDID. However, it's completely broken if there are
invalid extensions in the middle; the invalid blocks are included and
valid blocks are excluded.

Fix it by modifying the base block after, not before, the copy.

Fixes: 14544d0937bf ("drm/edid: Only print the bad edid when aborting")
Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/drm_edid.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index d79b06f7f34c..8829120470ab 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2031,9 +2031,6 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
 
 		connector_bad_edid(connector, edid, edid[0x7e] + 1);
 
-		edid[EDID_LENGTH-1] += edid[0x7e] - valid_extensions;
-		edid[0x7e] = valid_extensions;
-
 		new = kmalloc_array(valid_extensions + 1, EDID_LENGTH,
 				    GFP_KERNEL);
 		if (!new)
@@ -2050,6 +2047,9 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
 			base += EDID_LENGTH;
 		}
 
+		new[EDID_LENGTH - 1] += new[0x7e] - valid_extensions;
+		new[0x7e] = valid_extensions;
+
 		kfree(edid);
 		edid = new;
 	}
-- 
2.30.2