Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29ffe1...
Commit:     29ffe1a5c52dae13b6efead97aab9b058f38fce4
Parent:     1987e7b4855fcb6a866d3279ee9f2890491bc34d
Author:     Herbert Xu <herbert@gondor.apana.org.au>
AuthorDate: Mon Jan 28 20:45:20 2008 -0800
Committer:  David S. Miller <davem@davemloft.net>
CommitDate: Thu Jan 31 19:27:07 2008 -0800

    [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>
---
 net/ipv4/ip_output.c  |    4 +++-
 net/ipv6/ip6_output.c |    4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 18070ca..6e4d5f4 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 15c4f6c..cfe9e70 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));
-
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