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

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Message-ID: <20090225190218.GA7453@redhat.com>
Date:	Wed, 25 Feb 2009 20:02:18 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	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>,
	Roland McGrath <roland@...hat.com>,
	Tavis Ormandy <taviso@....lonestar.org>,
	Vitaly Mayatskikh <vmayatsk@...hat.com>, stable@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] exit_notify: kill the wrong capable(CAP_KILL) check

I can't understand why exit_notify() checks capable(CAP_KILL), but this
looks just wrong.

Whatever logic we have to reset ->exit_signal, the bad user can bypass
it if it execs the setuid application before exiting, kill the CAP_KILL
check.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- 6.29-rc3/kernel/exit.c~2_EXIT_NOTIFY	2009-02-13 07:04:12.000000000 +0100
+++ 6.29-rc3/kernel/exit.c	2009-02-25 19:41:57.000000000 +0100
@@ -874,8 +874,7 @@ static void exit_notify(struct task_stru
 	 */
 	if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
 	    (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
-	     tsk->self_exec_id != tsk->parent_exec_id) &&
-	    !capable(CAP_KILL))
+	     tsk->self_exec_id != tsk->parent_exec_id))
 		tsk->exit_signal = SIGCHLD;
 
 	signal = tracehook_notify_death(tsk, &cookie, group_dead);

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