8021q: fix a potential use-after-free

[ Upstream commit 4a7df340ed1bac190c124c1601bfc10cde9fb4fb ]

vlan_vid_del() could possibly free ->vlan_info after a RCU grace
period, however, we may still refer to the freed memory area
by 'grp' pointer. Found by code inspection.

This patch moves vlan_vid_del() as behind as possible.

Cc: Patrick McHardy <kaber@trash.net>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 5471628d3ffe73fd0f8b3cc8d3504cfeae78019c..963f285e69cae0d67181ec911b8b2e56dc7bc0e0 100644 (file)
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -110,13 +110,6 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
        grp = rtnl_dereference(real_dev->vlgrp);
        BUG_ON(!grp);
 
-       /* Take it out of our own structures, but be sure to interlock with
-        * HW accelerating devices or SW vlan input packet processing if
-        * VLAN is not 0 (leave it there for 802.1p).
-        */
-       if (vlan_id && (real_dev->features & NETIF_F_HW_VLAN_FILTER))
-               ops->ndo_vlan_rx_kill_vid(real_dev, vlan_id);
-
        grp->nr_vlans--;
 
        if (vlan->flags & VLAN_FLAG_GVRP)
@@ -139,6 +132,13 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
                call_rcu(&grp->rcu, vlan_rcu_free);
        }
 
+       /* Take it out of our own structures, but be sure to interlock with
+        * HW accelerating devices or SW vlan input packet processing if
+        * VLAN is not 0 (leave it there for 802.1p).
+        */
+       if (vlan_id && (real_dev->features & NETIF_F_HW_VLAN_FILTER))
+               ops->ndo_vlan_rx_kill_vid(real_dev, vlan_id);
+
        /* Get rid of the vlan's reference to real_dev */
        dev_put(real_dev);
 }