From 66e4c8d950083df8e12981babca788e1635c92b6 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 9 May 2022 20:57:39 -0700
Subject: [PATCH] net: warn if transport header was not set

Make sure skb_transport_header() and skb_transport_offset() uses
are not fooled if the transport header has not been set.

This change will likely expose existing bugs in linux networking stacks.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 include/linux/skbuff.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5296b2c37f62..b91d225fdc13 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -42,6 +42,7 @@
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 #include <linux/netfilter/nf_conntrack_common.h>
 #endif
+#include <net/net_debug.h>
 
 /**
  * DOC: skb checksums
@@ -2904,6 +2905,7 @@ static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
 
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 {
+	DEBUG_NET_WARN_ON_ONCE(!skb_transport_header_was_set(skb));
 	return skb->head + skb->transport_header;
 }