Subject: Re: Regression, bisected: reference leak with IPSec since ~2.6.31

From: Jarek Poplawski <[email-masked]>
Date: Tue, 21 Sep 2010 09:12:48 +0000

On 2010-09-20 23:31, Eric Dumazet wrote:
...
> [PATCH] ip : fix truesize mismatch in ip fragmentation
> 
> We should not set frag->destructor to sock_wkfree() until we are sure we
> dont hit slow path in ip_fragment(). Or we risk uncharging
> frag->truesize twice, and in the end, having negative socket
> sk_wmem_alloc counter, or even freeing socket sooner than expected.
> 
> Many thanks to Nick Bowler, who provided a very clean bug report and
> test programs.
> 
> While Nick bisection pointed to commit 2b85a34e911bf483 (net: No more
> expensive sock_hold()/sock_put() on each tx), underlying bug is older.
> 
> Reported-and-bisected-by: Nick Bowler <[email-masked]>
> Signed-off-by: Eric Dumazet <[email-masked]>
> ---
>  net/ipv4/ip_output.c  |    8 ++++----
>  net/ipv6/ip6_output.c |   10 +++++-----
>  2 files changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 04b6989..126d9b3 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -490,7 +490,6 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
>  	if (skb_has_frags(skb)) {
>  		struct sk_buff *frag;
>  		int first_len = skb_pagelen(skb);
> -		int truesizes = 0;
>  
>  		if (first_len - hlen > mtu ||
>  		    ((first_len - hlen) & 7) ||
> @@ -510,11 +509,13 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
>  				goto slow_path;
>  
>  			BUG_ON(frag->sk);
> -			if (skb->sk) {
> +		}
> +		if (skb->sk) {
> +			skb_walk_frags(skb, frag) {
>  				frag->sk = skb->sk;
>  				frag->destructor = sock_wfree;

Nice catch, but it seems doing it in the first loop as now, and
reverting changes before goto slow_path might be more optimal here.

Jarek P.