xfrm: check for a vaild skb in xfrm_policy_queue_process

We might dreference a NULL pointer if the hold_queue is empty,
so add a check to avoid this.

Bug was introduced with git commit a0073fe18 ("xfrm: Add a state
resolution packet queue")

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

1 files changed, 4 insertions, 0 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 5f9be976770e..76e1873811d4 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1772,6 +1772,10 @@ static void xfrm_policy_queue_process(unsigned long arg)
 
         spin_lock(&pq->hold_queue.lock);
         skb = skb_peek(&pq->hold_queue);
+        if (!skb) {
+                spin_unlock(&pq->hold_queue.lock);
+                goto out;
+        }
         dst = skb_dst(skb);
         sk = skb->sk;
         xfrm_decode_session(skb, &fl, dst->ops->family);