linux-kernel - Re: Q: selinux_bprm_committed_creds() && signals/do

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Date:	Wed, 29 Apr 2009 15:30:15 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	David Howells <dhowells@...hat.com>,
	Eric Paris <eparis@...isplace.org>,
	James Morris <jmorris@...ei.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Q: selinux_bprm_committed_creds() && signals/do_wait

On 04/29, Stephen Smalley wrote:
>
> 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/.

Great, thanks. Will send the patch soon.

Oleg.

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