linux-kernel - Re: [PATCH 2/2] exit_notify: kill the wrong capable(CAP

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Message-ID: <20090225215356.GA1442@hallyn.com>
Date:	Wed, 25 Feb 2009 15:53:56 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Chris Evans <scarybeasts@...il.com>,
	David Howells <dhowells@...hat.com>,
	Don Howard <dhoward@...hat.com>,
	Eugene Teo <eugene@...hat.com>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Tavis Ormandy <taviso@....lonestar.org>,
	Vitaly Mayatskikh <vmayatsk@...hat.com>, stable@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] exit_notify: kill the wrong capable(CAP_KILL) check

Quoting Roland McGrath (roland@...hat.com):
> > I can't understand why exit_notify() checks capable(CAP_KILL), but this
> > looks just wrong.
> 
> I don't know either why it's there.  My guess is that it was not actually
> thought out specifically, just a "unless capable" exception added when the
> security-motivated exclusions (exec_id stuff) were added.
> 
> I can't think of any reason not to drop this check.

Because of the following test?

#include <stdio.h>
#include <sched.h>
#include <signal.h>
#include <stdlib.h>

int childfn(void *data)
{
	printf("hi there, i'm the child\n");
	sleep(10);
	exit(0);
}

int main()
{
	int stacksize = 4*getpagesize();
	void *stack, *stacktop;

	stack = malloc(stacksize);
	stacktop = stack + stacksize;

	int p = clone(childfn, stacktop, CLONE_PARENT|SIGSTOP, NULL);
	exit(0);
}
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