[ 45/56] 8021q: fix a potential use-after-free

Greg Kroah-Hartman
2013-04-02T22:54:27Z

From: Cong Wang <amwang@redhat.com>

[ 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.

Signed-off-by: Cong Wang <amwang@redhat.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: "David S. Miller" <davem@davemloft.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/8021q/vlan.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -108,13 +108,6 @@ void unregister_vlan_dev(struct net_devi
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_devi
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);
}