netdev - Re: [PATCH 2/3] ipvs: add missing lock in ip_vs_ftp_init

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Message-ID: <CAJn8CcHPOMRt6SjP5YvH3=4UtihFJKbCOJP4TBcfzguPRxEggQ@mail.gmail.com>
Date:	Tue, 17 Jul 2012 10:34:43 +0800
From:	Xiaotian Feng <xtfeng@...il.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	Simon Horman <horms@...ge.net.au>, lvs-devel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	Wensong Zhang <wensong@...ux-vs.org>,
	Julian Anastasov <ja@....bg>,
	Hans Schillstrom <hans.schillstrom@...csson.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Xiaotian Feng <dannyfeng@...cent.com>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/3] ipvs: add missing lock in ip_vs_ftp_init_conn()

On Tue, Jul 17, 2012 at 5:07 AM, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> Hi Simon,
>
> On Wed, Jul 11, 2012 at 09:19:22AM +0900, Simon Horman wrote:
>> From: Xiaotian Feng <xtfeng@...il.com>
>>
>> We met a kernel panic in 2.6.32.43 kernel:
> [...]
>>  net/netfilter/ipvs/ip_vs_ftp.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
>> index b20b29c..c2bc264 100644
>> --- a/net/netfilter/ipvs/ip_vs_ftp.c
>> +++ b/net/netfilter/ipvs/ip_vs_ftp.c
>> @@ -65,8 +65,10 @@ static int ip_vs_ftp_pasv;
>>  static int
>>  ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
>>  {
>> +     spin_lock(&cp->lock);
>>       /* We use connection tracking for the command connection */
>>       cp->flags |= IP_VS_CONN_F_NFCT;
>> +     spin_unlock(&cp->lock);
>>       return 0;
>
> The conntrack support for FTP IPVS helper seems to be there since
> 2.6.37.
>
> However, the patch description mentions 2.6.32.43.
>
> Something doesn't match here, could you clarify this?
>

Sorry for the misleading description in the patch. We found the panic
in 2.6.32.43 is caused by changing cp->flags without protection. In
2.6.32.43, ip_vs_process_message changes cp->flags without protection
while update active/inactive flags for the connection.

After code inspiration, we found in 3.x kernel, it is accidentally
fixed by commit  f73181c. But with ip_vs_app changes,
ip_vs_ftp_init_conn() will have chance to change cp->flags without
protection. So it is a potential bug in 3.x kernel.


> Thanks.
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