[ 3.5.y.z extended stable ] Patch "8021q: fix a potential use-after-free" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    8021q: fix a potential use-after-free

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4405dfe7d19bd15f92654036016f3963103396f1 Mon Sep 17 00:00:00 2001
From: Cong Wang <amwang at redhat.com>
Date: Fri, 22 Mar 2013 19:14:07 +0000
Subject: [PATCH] 8021q: fix a potential use-after-free

commit 4a7df340ed1bac190c124c1601bfc10cde9fb4fb upstream.

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 at trash.net>
Cc: "David S. Miller" <davem at davemloft.net>
Signed-off-by: Cong Wang <amwang at redhat.com>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/8021q/vlan.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 9096bcb..8bdc56d 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_GVRP)
@@ -108,6 +101,13 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
 	if (grp->nr_vlan_devs == 0)
 		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);
 }
--
1.8.1.2