From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 29 Jan 2008 04:45:20 +0000 (-0800)
Subject: [INET]: Prevent out-of-sync truesize on ip_fragment slow path
X-Git-Tag: v2.6.25-rc1~1089^2~128
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29ffe1a5c52dae13b6efead97aab9b058f38fce4;p=linux-2.6

[INET]: Prevent out-of-sync truesize on ip_fragment slow path

When ip_fragment has to hit the slow path the value of skb->truesize
may go out of sync because we would have updated it without changing
the packet length.  This violates the constraints on truesize.

This patch postpones the update of skb->truesize to prevent this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 18070ca657..6e4d5f493b 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -476,6 +476,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 	if (skb_shinfo(skb)->frag_list) {
 		struct sk_buff *frag;
 		int first_len = skb_pagelen(skb);
+		int truesizes = 0;
 
 		if (first_len - hlen > mtu ||
 		    ((first_len - hlen) & 7) ||
@@ -499,7 +500,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 				sock_hold(skb->sk);
 				frag->sk = skb->sk;
 				frag->destructor = sock_wfree;
-				skb->truesize -= frag->truesize;
+				truesizes += frag->truesize;
 			}
 		}
 
@@ -510,6 +511,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 		frag = skb_shinfo(skb)->frag_list;
 		skb_shinfo(skb)->frag_list = NULL;
 		skb->data_len = first_len - skb_headlen(skb);
+		skb->truesize -= truesizes;
 		skb->len = first_len;
 		iph->tot_len = htons(first_len);
 		iph->frag_off = htons(IP_MF);
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 15c4f6cee3..cfe9e70788 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -636,6 +636,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 
 	if (skb_shinfo(skb)->frag_list) {
 		int first_len = skb_pagelen(skb);
+		int truesizes = 0;
 
 		if (first_len - hlen > mtu ||
 		    ((first_len - hlen) & 7) ||
@@ -658,7 +659,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 				sock_hold(skb->sk);
 				frag->sk = skb->sk;
 				frag->destructor = sock_wfree;
-				skb->truesize -= frag->truesize;
+				truesizes += frag->truesize;
 			}
 		}
 
@@ -689,6 +690,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 
 		first_len = skb_pagelen(skb);
 		skb->data_len = first_len - skb_headlen(skb);
+		skb->truesize -= truesizes;
 		skb->len = first_len;
 		ipv6_hdr(skb)->payload_len = htons(first_len -
 						   sizeof(struct ipv6hdr));