linux-kernel - Re: [PATCH 3/3] ptrace: do not use task

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Date:	Wed, 6 May 2009 16:27:03 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 3/3] ptrace: do not use task_lock() for attach

* Oleg Nesterov (oleg@...hat.com) wrote:
> But this can happen without this change too?
> 
> - cpu2 takes task_lock(), tracehook_tracer_task() returns NULL because
>   we are not traced yet.
> 
> - cpu1 does ptrace_attach() and succeds, because cpu2 didn't update sid
>   yet
> 
> - cpu2 continues, it doesn't check avc_has_perm() (tracer == 0) and
>   updates sid.
> 
> No?

Yes.

> Shouldn't selinux_setprocattr() take ->cred_exec_mutex, like we do in
> selinux_bprm_set_creds() path?

I was looking at the same, seems like it to me.  James?

thanks,
-chris
> 
> Oleg.
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