net: openvswitch: silence suspicious RCU usage warning

Silence suspicious RCU usage warning in ovs_flow_tbl_masks_cache_resize()
by replacing rcu_dereference() with rcu_dereference_ovsl().

In addition, when creating a new datapath, make sure it's configured under
the ovs_lock.

Fixes: 9bf24f5 ("net: openvswitch: make masks cache size configurable")
Reported-by: syzbot+9a8f8bfcc56e8578016c@syzkaller.appspotmail.com
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Link: https://lore.kernel.org/r/160439190002.56943.1418882726496275961.stgit@ebuild
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/openvswitch/datapath.c

@@ -1703,13 +1703,13 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 	parms.port_no = OVSP_LOCAL;
 	parms.upcall_portids = a[OVS_DP_ATTR_UPCALL_PID];
 
-	err = ovs_dp_change(dp, a);
-	if (err)
-		goto err_destroy_meters;
-
 	/* So far only local changes have been made, now need the lock. */
 	ovs_lock();
 
+	err = ovs_dp_change(dp, a);
+	if (err)
+		goto err_unlock_and_destroy_meters;
+
 	vport = new_vport(&parms);
 	if (IS_ERR(vport)) {
 		err = PTR_ERR(vport);
@@ -1725,8 +1725,7 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 				ovs_dp_reset_user_features(skb, info);
 		}
 
-		ovs_unlock();
-		goto err_destroy_meters;
+		goto err_unlock_and_destroy_meters;
 	}
 
 	err = ovs_dp_cmd_fill_info(dp, reply, info->snd_portid,
@@ -1741,7 +1740,8 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 	ovs_notify(&dp_datapath_genl_family, reply, info);
 	return 0;
 
-err_destroy_meters:
+err_unlock_and_destroy_meters:
+	ovs_unlock();
 	ovs_meters_exit(dp);
 err_destroy_ports:
 	kfree(dp->ports);

net/openvswitch/flow_table.c

@@ -390,7 +390,7 @@ static struct mask_cache *tbl_mask_cache_alloc(u32 size)
 }
 int ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size)
 {
-	struct mask_cache *mc = rcu_dereference(table->mask_cache);
+	struct mask_cache *mc = rcu_dereference_ovsl(table->mask_cache);
 	struct mask_cache *new;
 
 	if (size == mc->cache_size)