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Date:	Fri, 29 Jun 2012 09:50:59 +0800
From:	Xiaotian Feng <xtfeng@...il.com>
To:	Julian Anastasov <ja@....bg>
Cc:	netdev@...r.kernel.org, lvs-devel@...r.kernel.org,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, linux-kernel@...r.kernel.org,
	Xiaotian Feng <dannyfeng@...cent.com>,
	Wensong Zhang <wensong@...ux-vs.org>,
	Simon Horman <horms@...ge.net.au>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH net-next] ipvs: add missing lock in ip_vs_ftp_init_conn()

On Fri, Jun 29, 2012 at 8:17 AM, Julian Anastasov <ja@....bg> wrote:
>
>        Hello,
>
> On Thu, 28 Jun 2012, Xiaotian Feng wrote:
>
>> We met a kernel panic in 2.6.32.43 kernel:
>>
>> [2680191.848044] IPVS: ip_vs_conn_hash(): request for already hashed, called from run_timer_softirq+0x175/0x1d0
>> <snip>
>> [2680311.849009] general protection fault: 0000 [#1] SMP
>> [2680311.853001] RIP: 0010:[<ffffffff815f155c>]  [<ffffffff815f155c>] ip_vs_conn_expire+0xdc/0x2f0
>> [2680311.853001] RSP: 0018:ffff880028303e70  EFLAGS: 00010202
>> [2680311.853001] RAX: dead000000200200 RBX: ffff8801aad00b80 RCX: 0000000000001d90
>> [2680311.853001] RDX: dead000000100100 RSI: 000000004fd59800 RDI: ffff8801aad00c08
>> <snip>
>> [2680311.853001] Call Trace:
>> [2680311.853001]  <IRQ>
>> [2680311.853001]  [<ffffffff815f1480>] ? ip_vs_conn_expire+0x0/0x2f0
>> [2680311.853001]  [<ffffffff8104e2a5>] run_timer_softirq+0x175/0x1d0
>> [2680311.853001]  [<ffffffff81021a48>] ? lapic_next_event+0x18/0x20
>> [2680311.853001]  [<ffffffff81049a13>] __do_softirq+0xb3/0x150
>> [2680311.853001]  [<ffffffff8100cc5c>] call_softirq+0x1c/0x30
>> [2680311.853001]  [<ffffffff8100ea9a>] do_softirq+0x4a/0x80
>> [2680311.853001]  [<ffffffff81049957>] irq_exit+0x77/0x80
>> [2680311.853001]  [<ffffffff81021f2c>] smp_apic_timer_interrupt+0x6c/0xa0
>> [2680311.853001]  [<ffffffff8100c633>] apic_timer_interrupt+0x13/0x20
>> [2680311.853001]  <EOI>
>> [2680311.853001]  [<ffffffff81013b52>] ? mwait_idle+0x52/0x70
>> [2680311.853001]  [<ffffffff8100a7b0>] ? enter_idle+0x20/0x30
>> [2680311.853001]  [<ffffffff8100ac62>] ? cpu_idle+0x52/0x80
>> [2680311.853001]  [<ffffffff816d504d>] ? start_secondary+0x19d/0x280
>>
>> rax and rdx is LIST_POISON1 and LIST_POISON2, so kernel is list_del() on an already deleted
>> connection and result the general protect fault.
>>
>> The "request for already hashed" warning, told us someone might change the connection flags
>> incorrectly, like described in commit aea9d711, it changes the connection flags, but doesn't
>> put the connection back to the list. So ip_vs_conn_hash() throw a warning and return.
>> Later, when ip_vs_conn_expire fire again, ip_vs_conn_unhash() will find the HASHED connection
>> and list_del() it, then kernel panic happened.
>>
>> After code review, the only chance that kernel change connection flag without protection is
>> in ip_vs_ftp_init_conn().
>
>        Hm, ip_vs_ftp_init_conn is called before 1st hashing,
> from ip_vs_bind_app() in ip_vs_conn_new() before
> ip_vs_conn_hash(). It should be another problem with
> the flags. How different is IPVS in 2.6.32.43 compared to
> recent kernels? If commit aea9d711 is present, I'm not
> aware of other similar problems.

ip_vs_bind_app() is also called by ip_vs_try_bind_dest(), which can be
traced to ip_vs_proc_conn().
I've checked the changes in upstream, but nothing helps since aea9d711
has been taken into 2.6.32.28 kernel.

>
>        May be you can post some details for your setup on
> lvs-devel@...r.kernel.org. I assume FTP is used,
> what about master-backup sync? Can you confirm that
> this fix solves the problem or it happens in rare cases?

Yes, ftp and WRR scheduler is used. Unfortunately, the oops
is unreproducible :(

>
>> Signed-off-by: Xiaotian Feng <dannyfeng@...cent.com>
>> Cc: Wensong Zhang <wensong@...ux-vs.org>
>> Cc: Simon Horman <horms@...ge.net.au>
>> Cc: Julian Anastasov <ja@....bg>
>> Cc: Pablo Neira Ayuso <pablo@...filter.org>
>> Cc: Patrick McHardy <kaber@...sh.net>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> ---
>>  net/netfilter/ipvs/ip_vs_ftp.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> 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;
>>  }
>>
>> --
>> 1.7.1
>
> Regards
>
> --
> Julian Anastasov <ja@....bg>
--
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