[PATCH] drm/virtio: add driver_priv validation in virtio_gpu_create_context

[Maxim Korotkov]

The pointer file->driver_priv was dereferenced without checking
against NULL, but in the "virtio_gpu_transfer_to_host_ioctl" function
it was checked against NULL after calling virtio_gpu_create_context
function.

Found by Security Code and Linux Verification Center(linuxtesting.org)
Fixes: 72b48ae800da ("drm/virtio: enqueue virtio_gpu_create_context after the first 3D ioctl")
Signed-off-by: Maxim Korotkov <korotkov.maxim.s@xxxxxxxxx>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index e4f76f315550..98fe9ad4ed15 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -64,6 +64,9 @@ void virtio_gpu_create_context(struct drm_device *dev, struct drm_file *file)
 	struct virtio_gpu_device *vgdev = dev->dev_private;
 	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
 
+	if (!vfpriv)
+		return;
+
 	mutex_lock(&vfpriv->context_lock);
 	if (vfpriv->context_created)
 		goto out_unlock;
-- 
2.34.1