Subject: [net-next PATCH v2 2/8] udp: Verify that pulling UDP header in GSO segmentation doesn't fail

From: Alexander Duyck <[email-masked]>
Date: Fri, 04 May 2018 11:29:35 -0700

From: Alexander Duyck <[email-masked]>

We should verify that we can pull the UDP header before we attempt to do
so. Otherwise if this fails we have no way of knowing and GSO will not work
correctly.

Signed-off-by: Alexander Duyck <[email-masked]>
---

v2: New break-out patch based on one patch from earlier series

 net/ipv4/udp_offload.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 006257092f06..8303fff42940 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -191,14 +191,17 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 				  netdev_features_t features,
 				  unsigned int mss, __sum16 check)
 {
+	struct sk_buff *seg, *segs = ERR_PTR(-EINVAL);
 	struct sock *sk = gso_skb->sk;
 	unsigned int sum_truesize = 0;
-	struct sk_buff *segs, *seg;
 	unsigned int hdrlen;
 	struct udphdr *uh;
 
 	if (gso_skb->len <= sizeof(*uh) + mss)
-		return ERR_PTR(-EINVAL);
+		goto out;
+
+	if (!pskb_may_pull(gso_skb, sizeof(*uh)))
+		goto out;
 
 	hdrlen = gso_skb->data - skb_mac_header(gso_skb);
 	skb_pull(gso_skb, sizeof(*uh));
@@ -230,7 +233,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 	}
 
 	refcount_add(sum_truesize - gso_skb->truesize, &sk->sk_wmem_alloc);
-
+out:
 	return segs;
 }
 EXPORT_SYMBOL_GPL(__udp_gso_segment);