netdev-dpdk: Fix race condition in mempool information dump.

Currently it is possible to call netdev-dpdk/get-mempool-info before a
mempool as been created. This can happen because a device is added to
the netdev_shash before a mempool is allocated for it, which results in
a segmentation fault.

Now we check for a NULL value before attempting to dereference it.

Fixes: be48173 ("netdev-dpdk: Add debug appctl to get mempool information.")
Signed-off-by: Mike Pattrick <mkp@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

lib/netdev-dpdk.c

@@ -3834,10 +3834,11 @@ netdev_dpdk_get_mempool_info(struct unixctl_conn *conn,
                              int argc, const char *argv[],
                              void *aux OVS_UNUSED)
 {
-    size_t size;
-    FILE *stream;
-    char *response = NULL;
     struct netdev *netdev = NULL;
+    const char *error = NULL;
+    char *response = NULL;
+    FILE *stream;
+    size_t size;
 
     if (argc == 2) {
         netdev = netdev_from_name(argv[1]);
@@ -3861,10 +3862,14 @@ netdev_dpdk_get_mempool_info(struct unixctl_conn *conn,
         ovs_mutex_lock(&dev->mutex);
         ovs_mutex_lock(&dpdk_mp_mutex);
 
-        rte_mempool_dump(stream, dev->dpdk_mp->mp);
-        fprintf(stream, "    count: avail (%u), in use (%u)\n",
-                rte_mempool_avail_count(dev->dpdk_mp->mp),
-                rte_mempool_in_use_count(dev->dpdk_mp->mp));
+        if (dev->dpdk_mp) {
+            rte_mempool_dump(stream, dev->dpdk_mp->mp);
+            fprintf(stream, "    count: avail (%u), in use (%u)\n",
+                    rte_mempool_avail_count(dev->dpdk_mp->mp),
+                    rte_mempool_in_use_count(dev->dpdk_mp->mp));
+        } else {
+            error = "Not allocated";
+        }
 
         ovs_mutex_unlock(&dpdk_mp_mutex);
         ovs_mutex_unlock(&dev->mutex);
@@ -3876,7 +3881,11 @@ netdev_dpdk_get_mempool_info(struct unixctl_conn *conn,
 
     fclose(stream);
 
-    unixctl_command_reply(conn, response);
+    if (error) {
+        unixctl_command_reply_error(conn, error);
+    } else {
+        unixctl_command_reply(conn, response);
+    }
 out:
     free(response);
     netdev_close(netdev);

tests/system-dpdk.at

@@ -82,6 +82,12 @@ AT_CHECK([grep "VHOST_CONFIG: vhost-user client: socket created" ovs-vswitchd.lo
 AT_CHECK([grep "vHost User device 'dpdkvhostuserclient0' created in 'client' mode, using client socket" ovs-vswitchd.log], [], [stdout])
 AT_CHECK([grep "VHOST_CONFIG: $OVS_RUNDIR/dpdkvhostclient0: reconnecting..." ovs-vswitchd.log], [], [stdout])
 
+dnl Check that no mempool was allocated.
+AT_CHECK([ovs-appctl netdev-dpdk/get-mempool-info dpdkvhostuserclient0], [2], [], [dnl
+Not allocated
+ovs-appctl: ovs-vswitchd: server returned an error
+])
+
 dnl Clean up
 AT_CHECK([ovs-vsctl del-port br10 dpdkvhostuserclient0], [], [stdout], [stderr])
 OVS_VSWITCHD_STOP("m4_join([], [SYSTEM_DPDK_ALLOWED_LOGS], [