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>

1 files changed, 1 insertions, 8 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index e52cab3591dd..f77c371ea72b 100644
--- 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);