netdev - Re: [PATCH ipsec v2] xfrm: check MAC header is shown with both skb->mac_len and skb_mac_header_was

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Message-ID: <CANn89i+4c0iLXXjFpD1OWV7OBHr5w4S975MKRVB9VU2L-htm4w@mail.gmail.com>
Date: Wed, 2 Oct 2024 14:59:24 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: En-Wei WU <en-wei.wu@...onical.com>
Cc: Peter Seiderer <ps.report@....net>, steffen.klassert@...unet.com, 
	herbert@...dor.apana.org.au, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	kai.heng.feng@...onical.com, chia-lin.kao@...onical.com, 
	anthony.wong@...onical.com, kuan-ying.lee@...onical.com, 
	chris.chiu@...onical.com
Subject: Re: [PATCH ipsec v2] xfrm: check MAC header is shown with both
 skb->mac_len and skb_mac_header_was_set()

On Wed, Oct 2, 2024 at 12:40 PM En-Wei WU <en-wei.wu@...onical.com> wrote:
>
> Hi,
>
> I would kindly ask if there is any progress :)

Can you now try this debug patch (with CONFIG_DEBUG_NET=y ) :

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 39f1d16f362887821caa022464695c4045461493..e0e4154cbeb90474d92634d505869526c566f132
100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2909,9 +2909,19 @@ static inline void
skb_reset_inner_headers(struct sk_buff *skb)
        skb->inner_transport_header = skb->transport_header;
 }

+static inline int skb_mac_header_was_set(const struct sk_buff *skb)
+{
+       return skb->mac_header != (typeof(skb->mac_header))~0U;
+}
+
 static inline void skb_reset_mac_len(struct sk_buff *skb)
 {
-       skb->mac_len = skb->network_header - skb->mac_header;
+       if (!skb_mac_header_was_set(skb)) {
+               DEBUG_NET_WARN_ON_ONCE(1);
+               skb->mac_len = 0;
+       } else {
+               skb->mac_len = skb->network_header - skb->mac_header;
+       }
 }

 static inline unsigned char *skb_inner_transport_header(const struct sk_buff
@@ -3014,11 +3024,6 @@ static inline void
skb_set_network_header(struct sk_buff *skb, const int offset)
        skb->network_header += offset;
 }

-static inline int skb_mac_header_was_set(const struct sk_buff *skb)
-{
-       return skb->mac_header != (typeof(skb->mac_header))~0U;
-}
-
 static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
 {
        DEBUG_NET_WARN_ON_ONCE(!skb_mac_header_was_set(skb));
@@ -3043,6 +3048,7 @@ static inline void skb_unset_mac_header(struct
sk_buff *skb)

 static inline void skb_reset_mac_header(struct sk_buff *skb)
 {
+       DEBUG_NET_WARN_ON_ONCE(skb->data < skb->head);
        skb->mac_header = skb->data - skb->head;
 }

@@ -3050,6 +3056,7 @@ static inline void skb_set_mac_header(struct
sk_buff *skb, const int offset)
 {
        skb_reset_mac_header(skb);
        skb->mac_header += offset;
+       DEBUG_NET_WARN_ON_ONCE(skb_mac_header(skb) < skb->head);
 }

 static inline void skb_pop_mac_header(struct sk_buff *skb)