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Subject: Re: Q: selinux_bprm_committed_creds() && signals/do_wait
From: Stephen Smalley <sds@tycho.nsa.gov>
To: Oleg Nesterov <oleg@redhat.com>
Cc: David Howells <dhowells@redhat.com>, Eric Paris <eparis@parisplace.org>,
       James Morris <jmorris@namei.org>, Roland McGrath <roland@redhat.com>,
       linux-kernel@vger.kernel.org
In-Reply-To: <20090428223025.GA11997@redhat.com>
References: <20090428223025.GA11997@redhat.com>
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Organization: National Security Agency
Date: Wed, 29 Apr 2009 09:18:36 -0400
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On Wed, 2009-04-29 at 00:30 +0200, Oleg Nesterov wrote:
> selinux_bprm_committed_creds:
> 
> 	rc = avc_has_perm()
> 	if (rc) {
> 		flush_signals(current);
> 
> This doesn't look right. If the task was SIGKILL'ed we must not proceed,
> the task should die. The fix is simple, we should check SIGNAL_GROUP_EXIT
> and do nothing in this case, the task will exit before return to user
> space. If SIGNAL_GROUP_EXIT is set, it is just wrong to drop SIGKILL and
> continue.
> 
> But, before fixing, I'd like to understand why we are doing
> 
> 		flush_signal_handlers(current, 1);
> 		sigemptyset(&current->blocked);
> 
> later. Could someone explain ? This looks unneeded.
> 
> 
> Another question,
> 
> 	wake_up_interruptible(&current->parent->signal->wait_chldexit);
> 
> Shouldn't we use ->real_parent ? Afaics, we shouldn't worry about the tracer
> if current is ptraced, exec must not succeed if the tracer has no rights to
> trace this task after cred changing. But we should notify ->real_parent which
> is, well, real parent.

That makes sense to me - yes, s/parent/real_parent/.

-- 
Stephen Smalley
National Security Agency