net: warn if transport header was not set

edumazet · davem330 · commit 66e4c8d95008 · 2022-05-11T12:44:16.000+01:00
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 &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git 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;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -42,6 +42,7 @@`
`42`	`42`	`#if IS_ENABLED(CONFIG_NF_CONNTRACK)`
`43`	`43`	`#include <linux/netfilter/nf_conntrack_common.h>`
`44`	`44`	`#endif`
	`45`	`+#include <net/net_debug.h>`
`45`	`46`
`46`	`47`	`/**`
`47`	`48`	`* DOC: skb checksums`
`@@ -2904,6 +2905,7 @@ static inline bool skb_transport_header_was_set(const struct sk_buff *skb)`
`2904`	`2905`
`2905`	`2906`	`static inline unsigned char skb_transport_header(const struct sk_buff skb)`
`2906`	`2907`	`{`
	`2908`	`+ DEBUG_NET_WARN_ON_ONCE(!skb_transport_header_was_set(skb));`
`2907`	`2909`	`return skb->head + skb->transport_header;`
`2908`	`2910`	`}`
`2909`	`2911`