From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jarek Poplawski <jarkao2@gmail.com>
Cc: Nick Bowler <nbowler@elliptictech.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>
Subject: Re: Regression, bisected: reference leak with IPSec since ~2.6.31
Date: Tue, 21 Sep 2010 13:58:30 +0200 [thread overview]
Message-ID: <1285070310.2617.359.camel@edumazet-laptop> (raw)
In-Reply-To: <20100921104821.GA8986@ff.dom.local>
Le mardi 21 septembre 2010 à 10:48 +0000, Jarek Poplawski a écrit :
> But if you were honest about caches there is no reason to be smart
> no more. ;-)
>
> Below is your patch mostly as an example only that I didn't mean
> nothing complex (ipv4 only, not compiled).
>
> Jarek P.
> ---
>
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 04b6989..049d61f 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) ||
> @@ -503,18 +502,18 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
> if (frag->len > mtu ||
> ((frag->len & 7) && frag->next) ||
> skb_headroom(frag) < hlen)
> - goto slow_path;
> + goto slow_path_clean;
>
> /* Partially cloned skb? */
> if (skb_shared(frag))
> - goto slow_path;
> + goto slow_path_clean;
>
> BUG_ON(frag->sk);
> if (skb->sk) {
> frag->sk = skb->sk;
> frag->destructor = sock_wfree;
> + skb->truesize -= frag->truesize;
> }
> - truesizes += frag->truesize;
> }
>
> /* Everything is OK. Generate! */
> @@ -524,7 +523,6 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
> frag = skb_shinfo(skb)->frag_list;
> skb_frag_list_init(skb);
> 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);
> @@ -576,6 +574,17 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
> }
> IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
> return err;
> +
> +slow_path_clean:
> + if (skb->sk) {
> + skb_walk_frags(skb, frag) {
> + if (!frag->sk)
> + break;
> + frag->sk = NULL;
> + frag->destructor = NULL;
> + skb->truesize += frag->truesize;
> + }
> + }
> }
>
> slow_path:
Nice try, but this adds a bug unfortunately, or if you prefer makes the
"BUG_ON(frag->sk);" being not fully covered.
If we hit slow path, and one or more frags had frag->sk set, we silently
unset it, instead of a nice BUG_ON().
If you really want to have a slow_path_clean, you should use a different
frag2 iterator :
slow_path_clean:
if (skb->sk) {
skb_walk_frags(skb, frag2) {
if (frag2 == frag)
break;
frag2->sk = NULL;
frag2->destructor = NULL;
skb->truesize += frag2->truesize;
}
}
Face it, this is too complex for net-2.6, could we just fix the bug, and
'optimize' later ?
next prev parent reply other threads:[~2010-09-21 11:58 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-20 17:44 Regression, bisected: reference leak with IPSec since ~2.6.31 Nick Bowler
2010-09-20 18:20 ` Eric Dumazet
2010-09-20 19:52 ` Nick Bowler
2010-09-20 20:00 ` David Miller
2010-09-20 21:23 ` Nick Bowler
2010-09-20 20:17 ` Eric Dumazet
2010-09-20 21:31 ` Eric Dumazet
2010-09-21 6:16 ` [PATCH] ip : take care of last fragment in ip_append_data Eric Dumazet
2010-09-21 23:38 ` David Miller
2010-09-22 4:44 ` Eric Dumazet
2010-09-22 4:53 ` David Miller
2010-09-24 21:42 ` David Miller
2010-09-21 9:12 ` Regression, bisected: reference leak with IPSec since ~2.6.31 Jarek Poplawski
2010-09-21 9:21 ` Eric Dumazet
2010-09-21 9:38 ` Jarek Poplawski
2010-09-21 9:55 ` Eric Dumazet
2010-09-21 10:07 ` Eric Dumazet
2010-09-21 10:48 ` Jarek Poplawski
2010-09-21 11:58 ` Eric Dumazet [this message]
2010-09-21 12:39 ` Jarek Poplawski
2010-09-21 14:05 ` Nick Bowler
2010-09-21 14:16 ` [PATCH] ip : fix truesize mismatch in ip fragmentation Eric Dumazet
2010-09-21 15:58 ` [PATCH v3] ip: " Eric Dumazet
2010-09-21 16:26 ` Henrique de Moraes Holschuh
2010-09-21 16:31 ` Eric Dumazet
2010-09-21 18:09 ` Henrique de Moraes Holschuh
2010-09-21 19:24 ` David Miller
2010-09-21 23:06 ` Henrique de Moraes Holschuh
2010-09-21 17:50 ` Jarek Poplawski
2010-09-21 18:47 ` Eric Dumazet
2010-09-21 19:21 ` Jarek Poplawski
2010-09-21 22:15 ` David Miller
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