drm/amdgpu: Validate VM ioctl flags.

None have been defined yet, so reject anybody setting any. Mesa sets
it to 0 anyway.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -2370,6 +2370,10 @@ int amdgpu_vm_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 	struct amdgpu_fpriv *fpriv = filp->driver_priv;
 	int r;
 
+	/* No valid flags defined yet */
+	if (args->in.flags)
+		return -EINVAL;
+
 	switch (args->in.op) {
 	case AMDGPU_VM_OP_RESERVE_VMID:
 		/* We only have requirement to reserve vmid from gfxhub */