netdev - [PATCH net-next 5/7] net: add debug check in skb_reset_transport

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Message-ID: <20241105174403.850330-6-edumazet@google.com>
Date: Tue,  5 Nov 2024 17:44:01 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/7] net: add debug check in skb_reset_transport_header()

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

This needs CONFIG_DEBUG_NET=y.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/skbuff.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 32a7d8a65b9f8f6087007177e763dc9498215e34..f76524844e7edc5fe4e0afc27ce71eed7fbd40f9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3007,7 +3007,10 @@ static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 
 static inline void skb_reset_transport_header(struct sk_buff *skb)
 {
-	skb->transport_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->transport_header))offset);
+	skb->transport_header = offset;
 }
 
 static inline void skb_set_transport_header(struct sk_buff *skb,
-- 
2.47.0.199.ga7371fff76-goog