From: Patrick McHardy <kaber@trash.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>,
Thomas Gleixner <tglx@linutronix.de>,
torvalds@linux-foundation.org, akpm@linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30 __list_add+0x7d/0xad()
Date: Wed, 17 Jun 2009 14:00:04 +0200 [thread overview]
Message-ID: <4A38DAC4.2050902@trash.net> (raw)
In-Reply-To: <4A38D9BE.3020403@gmail.com>
Eric Dumazet wrote:
> Patrick McHardy a écrit :
>> Before the conntrack is confirmed, it is exclusively handled by a
>> single CPU. I agree that we need to make sure the IPS_CONFIRMED_BIT
>> is visible before we add the conntrack to the hash table since the
>> lookup is lockless, but simply moving the set_bit before the hash
>> insertion should be fine I think.
>>
>
> Hmm... now we could have the reverse case :
>
> __nf_conntrack_confirm() could be "interrupted" by __nf_ct_refresh_acct()
>
> index 5f72b94..22755fa 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -425,6 +425,7 @@ __nf_conntrack_confirm(struct sk_buff *skb)
> /* Remove from unconfirmed list */
> hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
>
> + set_bit(IPS_CONFIRMED_BIT, &ct->status);
> __nf_conntrack_hash_insert(ct, hash, repl_hash);
> /* Timer relative to confirmation time, not original
> setting time, otherwise we'd get timer wrap in
> @@ -432,7 +433,6 @@ __nf_conntrack_confirm(struct sk_buff *skb)
> ct->timeout.expires += jiffies;
>
> << What happens if another packet is handled by __nf_ct_refresh_acct here >>
> (seeing or not the IPS_CONFIRMED_BIT) >>
>
> add_timer(&ct->timeout);
>
> << or here ? >>
>
>
> atomic_inc(&ct->ct_general.use);
> - set_bit(IPS_CONFIRMED_BIT, &ct->status);
> NF_CT_STAT_INC(net, insert);
> spin_unlock_bh(&nf_conntrack_lock);
> help = nfct_help(ct);
>
> Problem is timeout.expires is either a relative or absolute timeout, and changes happen
> in __nf_conntrack_confirm() or __nf_ct_refresh_acct().
>
> We must have a synchronization (an barriers), a single bit wont be enough.
Please have a look at the second patch I just sent. It relies
on the RCU barriers to make sure all stores are visible before
other CPUs can find the conntrack.
next prev parent reply other threads:[~2009-06-17 12:00 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-15 12:04 [GIT]: Networking David Miller
2009-06-16 9:15 ` Ingo Molnar
2009-06-16 9:19 ` David Miller
2009-06-16 9:33 ` Ingo Molnar
2009-06-16 9:44 ` Ingo Molnar
2009-06-16 9:44 ` Alan Cox
2009-06-16 9:48 ` Ingo Molnar
2009-06-16 9:56 ` David Miller
2009-06-16 10:11 ` Ingo Molnar
2009-06-16 10:35 ` David Miller
2009-06-16 13:38 ` Eric Dumazet
2009-06-16 14:19 ` Eric Dumazet
2009-06-16 18:59 ` Linus Torvalds
2009-06-16 19:08 ` David Miller
2009-06-16 19:37 ` Eric Dumazet
2009-06-16 20:12 ` Eric Dumazet
2009-06-17 6:41 ` [PATCH] net: correct off-by-one write allocations reports Eric Dumazet
2009-06-17 11:31 ` [PATCH] atm: sk_wmem_alloc initial value is one Eric Dumazet
2009-06-18 2:06 ` David Miller
2009-06-18 2:05 ` [PATCH] net: correct off-by-one write allocations reports David Miller
2009-06-17 11:32 ` [GIT]: Networking David Miller
2009-06-16 9:21 ` David Miller
2009-06-16 9:26 ` Ingo Molnar
2009-06-16 10:47 ` David Miller
2009-06-16 10:53 ` Ingo Molnar
2009-06-16 12:24 ` Ingo Molnar
2009-06-16 12:39 ` David Miller
2009-06-17 9:21 ` [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30 __list_add+0x7d/0xad() Ingo Molnar
2009-06-17 10:18 ` Eric Dumazet
2009-06-17 11:08 ` Ingo Molnar
2009-06-17 11:35 ` David Miller
2009-06-18 5:23 ` Ingo Molnar
2009-06-18 5:58 ` Eric Dumazet
2009-06-18 9:47 ` Patrick McHardy
2009-06-18 14:56 ` Patrick McHardy
2009-06-18 15:46 ` Eric Dumazet
2009-06-18 16:09 ` Patrick McHardy
2009-06-18 16:13 ` Pablo Neira Ayuso
2009-06-18 22:46 ` [PATCH] netfilter: conntrack: death_by_timeout() fix Eric Dumazet
2009-06-19 11:15 ` Patrick McHardy
2009-06-20 15:47 ` [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30 __list_add+0x7d/0xad() Ingo Molnar
2009-06-20 15:56 ` Patrick McHardy
2009-06-17 11:38 ` Patrick McHardy
2009-06-17 11:51 ` Patrick McHardy
2009-06-17 11:55 ` Eric Dumazet
2009-06-17 12:00 ` Patrick McHardy [this message]
2009-06-17 12:33 ` Eric Dumazet
2009-06-17 12:36 ` Patrick McHardy
2009-06-17 13:27 ` Eric Dumazet
2009-06-17 13:29 ` Patrick McHardy
2009-06-17 14:23 ` Patrick McHardy
2009-06-17 15:29 ` Eric Dumazet
2009-06-17 15:34 ` Patrick McHardy
2009-06-18 23:18 ` [GIT]: Networking Tilman Schmidt
2009-06-19 3:36 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4A38DAC4.2050902@trash.net \
--to=kaber@trash.net \
--cc=akpm@linux-foundation.org \
--cc=davem@davemloft.net \
--cc=eric.dumazet@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=netdev@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).