[PATCH v3] drm/amdgpu: fix a possible null pointer dereference

[Ma Ke]

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

Cc: stable at vger.kernel.org
Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Signed-off-by: Ma Ke <make24 at iscas.ac.cn>
---
Changes in v3:
- added Cc stable line.
Changes in v2:
- modified the patch according to suggestions;
- added Fixes line.
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 9caba10315a8..25b51b600f6f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -458,6 +458,9 @@ static void amdgpu_connector_add_common_modes(struct drm_encoder *encoder,
 			continue;
 
 		mode = drm_cvt_mode(dev, common_modes[i].w, common_modes[i].h, 60, false, false, false);
+		if (!mode)
+			return;
+
 		drm_mode_probed_add(connector, mode);
 	}
 }
-- 
2.25.1