drm/msm/gem: fix error handling in msm_ioctl_gem_info_get_metadata()

msm_ioctl_gem_info_get_metadata() always returns 0 regardless of errors. When copy_to_user() fails or the user buffer is too small, the error code stored in ret is ignored because the function unconditionally returns 0. This causes userspace to believe the ioctl succeeded when it did not.

Additionally, kmemdup() can return NULL on allocation failure, but the return value is not checked. This leads to a NULL pointer dereference in the subsequent copy_to_user() call.

Add the missing NULL check for kmemdup() and return ret instead of 0.

Note that the SET counterpart (msm_ioctl_gem_info_set_metadata) correctly returns ret.

---
 drivers/gpu/drm/msm/msm_drv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index e5ab1e28851d..195f40e331e5 100644
@@ -536,6 +536,11 @@ static int msm_ioctl_gem_info_get_metadata(struct drm_gem_object *obj,
 	len = msm_obj->metadata_size;
 	buf = kmemdup(msm_obj->metadata, len, GFP_KERNEL);
 
+	if (!buf) {
+		msm_gem_unlock(obj);
+		return -ENOMEM;
+	}
+
 	msm_gem_unlock(obj);
 
 	if (*metadata_size < len) {

@@ -548,7 +553,7 @@ static int msm_ioctl_gem_info_get_metadata(struct drm_gem_object *obj,
 
 	kfree(buf);
 
-	return 0;
+	return ret;
 }
 
 static int msm_ioctl_gem_info(struct drm_device *dev, void *data,

2.50.1