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

[Chia-I Wu]

On Sat, Mar 26, 2022 at 10:09 PM Xiaomeng Tong <xiam0nd.tong at gmail.com> wrote:
>
> '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.tong at gmail.com>
Reviewed-by: Chia-I Wu <olvaffe at 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
>