linux-kernel - Re: Audit vs netlink interaction problem

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Date:	Mon, 17 Mar 2008 10:59:41 +0300
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	Thomas Graf <tgraf@...g.ch>
CC:	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: Audit vs netlink interaction problem

Thomas Graf wrote:
> * Pavel Emelyanov <xemul@...nvz.org> 2008-03-14 20:05
>> Hmmm... I'm afraid, that this can break the audit filtering and signal
>> auditing. I haven't yet looked deep into it, but it compares the 
>> task->tgid with this audit_pid for different purposes. If audit_pid
>> changes this code will be broken.
> 
> OK, then both pids have to be stored. audit_pid remains as-is but is
> no longer used as destination netlink pid. A second pid is stored and
> updated whenever a netlink message is received from userspace.
> 
>> Bu we have no the netlink socket at the moment of setting the pid to
>> check this. The audit_reveive_msg() call which does this set is received 
>> via another (pre-created global) socket.
> 
> I don't understand this. As far as I can read the code, a plain kernel
> side netlink socket is created in audit_init(). But it doesn't matter,
> as soon as we receive the first message from userspace, we know the
> netlink source pid.

audit_init() creates a kernel-side socket, while we need to know the pid 
of a user-side one. But I saw your patch, seems like the NETLINK_CB(skb).pid
is what we need for this check :)

>> I though, that proper behavior would be to split audit_pid, used for
>> filtering from the audit_nlk_pid used for netlink communications.
> 
> Yes, exactly.
> 

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