xfrm: Fix potential null pointer dereference in xdst_queue_output

The net_device might be not set on the skb when we try refcounting.
This leads to a null pointer dereference in xdst_queue_output().
It turned out that the refcount to the net_device is not needed
after all. The dst_entry has a refcount to the net_device before
we queue the skb, so it can't go away. Therefore we can remove the
refcount on queueing to fix the null pointer dereference.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index e52cab3591dd78c373274bb64420f87383775e8c..f77c371ea72b9e1a3d239998bdeb91de7585cd3b 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -320,10 +320,8 @@ static void xfrm_queue_purge(struct sk_buff_head *list)
 {
        struct sk_buff *skb;
 
-       while ((skb = skb_dequeue(list)) != NULL) {
-               dev_put(skb->dev);
+       while ((skb = skb_dequeue(list)) != NULL)
                kfree_skb(skb);
-       }
 }
 
 /* Rule must be locked. Release descentant resources, announce
@@ -1758,7 +1756,6 @@ static void xfrm_policy_queue_process(unsigned long arg)
        struct sk_buff *skb;
        struct sock *sk;
        struct dst_entry *dst;
-       struct net_device *dev;
        struct xfrm_policy *pol = (struct xfrm_policy *)arg;
        struct xfrm_policy_queue *pq = &pol->polq;
        struct flowi fl;
@@ -1805,7 +1802,6 @@ static void xfrm_policy_queue_process(unsigned long arg)
                dst = xfrm_lookup(xp_net(pol), skb_dst(skb)->path,
                                  &fl, skb->sk, 0);
                if (IS_ERR(dst)) {
-                       dev_put(skb->dev);
                        kfree_skb(skb);
                        continue;
                }
@@ -1814,9 +1810,7 @@ static void xfrm_policy_queue_process(unsigned long arg)
                skb_dst_drop(skb);
                skb_dst_set(skb, dst);
 
-               dev = skb->dev;
                err = dst_output(skb);
-               dev_put(dev);
        }
 
        return;
@@ -1839,7 +1833,6 @@ static int xdst_queue_output(struct sk_buff *skb)
        }
 
        skb_dst_force(skb);
-       dev_hold(skb->dev);
 
        spin_lock_bh(&pq->hold_queue.lock);