[PATCH v3] drm/gma500: fix null pointer dereference in cdv_intel_lvds_get_modes

[Ma Ke]

In cdv_intel_lvds_get_modes(), the return value of drm_mode_duplicate()
is assigned to mode, which will lead to a NULL pointer dereference on
failure of drm_mode_duplicate(). Add a check to avoid npd.

Cc: stable at vger.kernel.org
Fixes: 6a227d5fd6c4 ("gma500: Add support for Cedarview")
Signed-off-by: Ma Ke <make24 at iscas.ac.cn>
---
Changes in v3:
- added the recipient's email address, due to the prolonged absence of a 
response from the recipients.
Changes in v2:
- modified the patch according to suggestions from other patchs;
- added Fixes line;
- added Cc stable;
- Link: https://lore.kernel.org/lkml/20240622072514.1867582-1-make24@iscas.ac.cn/T/
---
 drivers/gpu/drm/gma500/cdv_intel_lvds.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/gma500/cdv_intel_lvds.c b/drivers/gpu/drm/gma500/cdv_intel_lvds.c
index f08a6803dc18..3adc2c9ab72d 100644
--- a/drivers/gpu/drm/gma500/cdv_intel_lvds.c
+++ b/drivers/gpu/drm/gma500/cdv_intel_lvds.c
@@ -311,6 +311,9 @@ static int cdv_intel_lvds_get_modes(struct drm_connector *connector)
 	if (mode_dev->panel_fixed_mode != NULL) {
 		struct drm_display_mode *mode =
 		    drm_mode_duplicate(dev, mode_dev->panel_fixed_mode);
+		if (!mode)
+			return 0;
+
 		drm_mode_probed_add(connector, mode);
 		return 1;
 	}
-- 
2.25.1