vhost: fix crash on reconnect

[ upstream commit 3c929a0 ]

When the vhost-user frontend like Virtio-user tries to
reconnect to the restarted Vhost backend, the Vhost backend
segfaults when multiqueue is enabled.

This is caused by VHOST_USER_GET_VRING_BASE being called for
a virtqueue that has not been created before, causing a NULL
pointer dereferencing.

This patch adds the VHOST_USER_GET_VRING_BASE requests to
the list of requests that trigger queue pair allocations.

Fixes: 160cbc8 ("vhost: remove a hack on queue allocation")

Reported-by: Yinan Wang <yinan.wang@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Tested-by: Yinan Wang <yinan.wang@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>

lib/librte_vhost/vhost_user.c

@@ -2606,6 +2606,7 @@ vhost_user_check_and_alloc_queue_pair(struct virtio_net *dev,
 		break;
 	case VHOST_USER_SET_VRING_NUM:
 	case VHOST_USER_SET_VRING_BASE:
+	case VHOST_USER_GET_VRING_BASE:
 	case VHOST_USER_SET_VRING_ENABLE:
 		vring_idx = msg->payload.state.index;
 		break;