[PATCH v2] drm/qxl: fix null pointer dereference in qxl_add_mode

[Ma Ke <make24@xxxxxxxxxxx>]

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

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 1b043677d4be ("drm/qxl: add qxl_add_mode helper function")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
Changes in v2:
- added a blank line;
- added Cc line.
---
 drivers/gpu/drm/qxl/qxl_display.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index c6d35c33d5d6..c371ee59ab07 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -236,6 +236,9 @@ static int qxl_add_mode(struct drm_connector *connector,
 		return 0;
 
 	mode = drm_cvt_mode(dev, width, height, 60, false, false, false);
+	if (!mode)
+		return -ENOMEM;
+
 	if (preferred)
 		mode->type |= DRM_MODE_TYPE_PREFERRED;
 	mode->hdisplay = width;
-- 
2.25.1