8021q: fix a potential use-after-free

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>

1 files changed, 7 insertions, 7 deletions

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index a18714469bf7..85addcd9372b 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -86,13 +86,6 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
 
         grp = &vlan_info->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)
-                vlan_vid_del(real_dev, vlan_id);
-
         grp->nr_vlan_devs--;
 
         if (vlan->flags & VLAN_FLAG_MVRP)
@@ -114,6 +107,13 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
                 vlan_gvrp_uninit_applicant(real_dev);
         }
 
+        /* 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)
+                vlan_vid_del(real_dev, vlan_id);
+
         /* Get rid of the vlan's reference to real_dev */
         dev_put(real_dev);
 }