net: add debug check in skb_reset_inner_transport_header()

Make sure (skb->data - skb->head) can fit in skb->inner_transport_header

This needs CONFIG_DEBUG_NET=y.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Link: https://patch.msgid.link/20241105174403.850330-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5d8fefa71cac78d83b9565d9038c319112da1e2d..75795568803c0bfc83652ea69e27521eeeaf5d40 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2937,7 +2937,10 @@ static inline int skb_inner_transport_offset(const struct sk_buff *skb)
 
 static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
 {
-       skb->inner_transport_header = skb->data - skb->head;
+       long offset = skb->data - skb->head;
+
+       DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->inner_transport_header))offset);
+       skb->inner_transport_header = offset;
 }
 
 static inline void skb_set_inner_transport_header(struct sk_buff *skb,