um: virtio_uml: free command if adding to virtqueue failed

If adding the command fails (i.e. the virtqueue is broken) then free it
again if the function allocated a new buffer for it.

Fixes: 68f5d3f3b6 ("um: add PCI over virtio emulation driver")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/virt-pci.c

@@ -137,8 +137,11 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 				out ? 1 : 0,
 				posted ? cmd : HANDLE_NO_FREE(cmd),
 				GFP_ATOMIC);
-	if (ret)
+	if (ret) {
+		if (posted)
+			kfree(cmd);
 		goto out;
+	}
 
 	if (posted) {
 		virtqueue_kick(dev->cmd_vq);