[PATCH 5.13 082/300] drm/gma500: Fix end of loop tests for list_for_each_entry

[Greg Kroah-Hartman]

From: Harshvardhan Jha <harshvardhan.jha@xxxxxxxxxx>

[ Upstream commit ea9a897b8affa0f7b4c90182b785dded74e434aa ]

The list_for_each_entry() iterator, "connector" in this code, can never be
NULL.  If we exit the loop without finding the correct  connector then
"connector" points invalid memory that is an offset from the list head.
This will eventually lead to memory corruption and presumably a kernel
crash.

Fixes: 9bd81acdb648 ("gma500: Convert Oaktrail to work with new output handling")
Signed-off-by: Harshvardhan Jha <harshvardhan.jha@xxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20210709073959.11443-1-harshvardhan.jha@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/gma500/oaktrail_lvds.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/oaktrail_lvds.c b/drivers/gpu/drm/gma500/oaktrail_lvds.c
index 432bdcc57ac9..a1332878857b 100644
--- a/drivers/gpu/drm/gma500/oaktrail_lvds.c
+++ b/drivers/gpu/drm/gma500/oaktrail_lvds.c
@@ -117,7 +117,7 @@ static void oaktrail_lvds_mode_set(struct drm_encoder *encoder,
 			continue;
 	}
 
-	if (!connector) {
+	if (list_entry_is_head(connector, &mode_config->connector_list, head)) {
 		DRM_ERROR("Couldn't find connector when setting mode");
 		gma_power_end(dev);
 		return;
-- 
2.30.2