[PATCH] drm: fix free illegal pointer when create drm_property_blob failed

[fuyufan]

From: fuyufan <fuyufan at huawei.com>

we get (Unable to handle kernel NULL pointer dereference at virtual
address 000000000000000c) when call drm_property_blob_put().
After analysis, we get the following process:

alloc faild:
drm_atomic_set_mode_for_crtc()
    drm_property_create_blob() // failed
    state->mode_blob = ERR_PTR(-ENOMEM)

free illegal pointer:
__drm_atomic_helper_crtc_destroy_state()
    drm_property_blob_put(state->mode_blob)
            drm_mode_object_put(&blob->base);   // here blob is ERR_PTR(-ENOMEM)

So do we have to determine if blob is an error code before calling drm_mode_object_put().

Signed-off-by: fuyufan <fuyufan at huawei.com>
---
 drivers/gpu/drm/drm_property.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_property.c b/drivers/gpu/drm/drm_property.c
index 69dfed57c..05dba22fe 100644
--- a/drivers/gpu/drm/drm_property.c
+++ b/drivers/gpu/drm/drm_property.c
@@ -597,7 +597,7 @@ EXPORT_SYMBOL(drm_property_create_blob);
  */
 void drm_property_blob_put(struct drm_property_blob *blob)
 {
-       if (!blob)
+       if (IS_ERR_OR_NULL(blob))
                return;

        drm_mode_object_put(&blob->base);
--
2.23.0