[PATCH v2 RESEND] drm/gma500: fix null pointer dereference in psb_intel_lvds_get_modes

[Ma Ke]

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

Cc: stable at vger.kernel.org
Fixes: 89c78134cc54 ("gma500: Add Poulsbo support")
Signed-off-by: Ma Ke <make24 at iscas.ac.cn>
---
Changes in v2:
- modified the patch according to suggestions;
- added Fixes line;
- added Cc stable.
---
 drivers/gpu/drm/gma500/psb_intel_lvds.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/gma500/psb_intel_lvds.c b/drivers/gpu/drm/gma500/psb_intel_lvds.c
index 8486de230ec9..8d1be94a443b 100644
--- a/drivers/gpu/drm/gma500/psb_intel_lvds.c
+++ b/drivers/gpu/drm/gma500/psb_intel_lvds.c
@@ -504,6 +504,9 @@ static int psb_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