From: Eric Dumazet <edumazet@google.com>
Date: Tue, 5 Nov 2024 17:44:00 +0000 (+0000)
Subject: net: add debug check in skb_reset_inner_mac_header()
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=78a0cb2f45dc9327f26956c242f7f4b450efff49;p=users%2Fjedix%2Flinux-maple.git

net: add debug check in skb_reset_inner_mac_header()

Make sure (skb->data - skb->head) can fit in skb->inner_mac_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/20241105174403.850330-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8dafd1295a6e..32a7d8a65b9f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2982,7 +2982,10 @@ static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
 
 static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
 {
-	skb->inner_mac_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->inner_mac_header))offset);
+	skb->inner_mac_header = offset;
 }
 
 static inline void skb_set_inner_mac_header(struct sk_buff *skb,