[PATCH] virtio-gpu: fix a missing check to avoid NULL dereference

[Xiaomeng Tong]

'cache_ent' could be set NULL inside virtio_gpu_cmd_get_capset()
and it will lead to a NULL dereference by a lately use of it
(i.e., ptr = cache_ent->caps_cache). Fix it with a NULL check.

Fixes: 62fb7a5e10962 ("virtio-gpu: add 3d/virgl support")
Signed-off-by: Xiaomeng Tong <xiam0nd.t...@gmail.com>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c 
b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index c708bab555c6..b0f1c4d8fd23 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -579,8 +579,10 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device 
*dev,
        spin_unlock(&vgdev->display_info_lock);
 
        /* not in cache - need to talk to hw */
-       virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
+       ret = virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
                                  &cache_ent);
+       if (ret)
+               return ret;
        virtio_gpu_notify(vgdev);
 
 copy_exit:

base-commit: f443e374ae131c168a065ea1748feac6b2e76613
-- 
2.17.1