netdev-dpdk: Restrict vhost_sock_dir

Since the vhost-user sockets directory now comes from the database, it is
possible for any user with database access to program an arbitrary filesystem
location for the sockets directory. This could result in unprivileged users
creating or deleting arbitrary filesystem files by using specially crafted
names. To prevent this, 'vhost-sock-dir' is now relative to ovs_rundir()
and must not contain "..".

Signed-off-by: Aaron Conole <aconole@redhat.com>
Acked-by: Daniele Di Proietto <diproiettod@vmware.com>

Author: apconole

lib/netdev-dpdk.c

@@ -2895,6 +2895,9 @@ dpdk_init__(const struct smap *ovs_other_config)
     int argc;
     int err;
     cpu_set_t cpuset;
+#ifndef VHOST_CUSE
+    char *sock_dir_subcomponent;
+#endif
 
     if (!smap_get_bool(ovs_other_config, "dpdk-init", false)) {
         VLOG_INFO("DPDK Disabled - to change this requires a restart.\n");
@@ -2907,15 +2910,29 @@ dpdk_init__(const struct smap *ovs_other_config)
     if (process_vhost_flags("cuse-dev-name", xstrdup("vhost-net"),
                             PATH_MAX, ovs_other_config, &cuse_dev_name)) {
 #else
-    if (process_vhost_flags("vhost-sock-dir", xstrdup(ovs_rundir()),
-                            NAME_MAX, ovs_other_config, &vhost_sock_dir)) {
+    if (process_vhost_flags("vhost-sock-dir", xstrdup(""),
+                            NAME_MAX, ovs_other_config,
+                            &sock_dir_subcomponent)) {
         struct stat s;
-
-        err = stat(vhost_sock_dir, &s);
-        if (err) {
-            VLOG_ERR("vhost-user sock directory '%s' does not exist.",
-                      vhost_sock_dir);
+        if (!strstr(sock_dir_subcomponent, "..")) {
+            vhost_sock_dir = xasprintf("%s/%s", ovs_rundir(),
+                                       sock_dir_subcomponent);
+
+            err = stat(vhost_sock_dir, &s);
+            if (err) {
+                VLOG_ERR("vhost-user sock directory '%s' does not exist.",
+                         vhost_sock_dir);
+            }
+        } else {
+            vhost_sock_dir = xstrdup(ovs_rundir());
+            VLOG_ERR("vhost-user sock directory request '%s/%s' has invalid"
+                     "characters '..' - using %s instead.",
+                     ovs_rundir(), sock_dir_subcomponent, ovs_rundir());
         }
+        free(sock_dir_subcomponent);
+    } else {
+        vhost_sock_dir = xstrdup(ovs_rundir());
+        free(sock_dir_subcomponent);
 #endif
     }
 

vswitchd/vswitch.xml

@@ -290,7 +290,9 @@
       <column name="other_config" key="vhost-sock-dir"
               type='{"type": "string"}'>
         <p>
-          Specifies the path to the vhost-user unix domain socket files.
+          Specifies the path to the vhost-user unix domain socket files. This
+          path must exist and be a subdirectory tree of the Open vSwitch
+          run directory.
         </p>
         <p>
           Defaults to the working directory of the application. Changing this