netdev - Re: xfrm_state locking regression...

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Message-ID: <48D8F337.2050103@iki.fi>
Date:	Tue, 23 Sep 2008 16:46:31 +0300
From:	Timo Teräs <timo.teras@....fi>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: xfrm_state locking regression...

Herbert Xu wrote:
> On Tue, Sep 23, 2008 at 04:30:06PM +0300, Timo Teräs wrote:
>> I have no strong opinion either way. So what ever you want, I'm
>> happy to provide a patch for.
> 
> Let's just leave it as it is for now.

Well, 1 is an improvement over the current implementation, so
I think it'd be better than not doing anything.

>>> What about xfrm_cfg_mutex?
>> It's used only in xfrm_state_gc_task. xfrm_state_walk_{init,done}
>> touch xfrm_state_walks list without locking properly. At least in
>> the version I'm looking (= net-next-2.6 via git web interface).
> 
> Their callers should be holding it.

Ah, the other layers take it at least on _walk_init paths. But
_walk_done can be called from recv() syscalls. The af_key
implementation does not take xfrm_cfg_mutex there. I don't think
xfrm_user does that either as it does not pass cb_mutex to
netlink_kernel_create. So at least the _state_walk_done path
is unsafe as-is, I think.

- Timo
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