[PATCH v2 RESEND] drm/client: fix null pointer dereference in drm_client_modeset_probe

[Ma Ke <make24@iscas.ac.cn>]

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

Cc: stable@vger.kernel.org
Fixes: cf13909aee05 ("drm/fb-helper: Move out modeset config code")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
Changes in v2:
- added the recipient's email address, due to the prolonged absence of a 
response from the recipients.
- added Cc stable.
---
 drivers/gpu/drm/drm_client_modeset.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
index 31af5cf37a09..cca37b225385 100644
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -880,6 +880,9 @@ int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width,
 
 			kfree(modeset->mode);
 			modeset->mode = drm_mode_duplicate(dev, mode);
+			if (!modeset->mode)
+				continue;
+
 			drm_connector_get(connector);
 			modeset->connectors[modeset->num_connectors++] = connector;
 			modeset->x = offset->x;
-- 
2.25.1