2009-04-06 14:21:23

by Oleg Nesterov

Subject: [PATCH, RESEND] exit_notify: kill the wrong capable(CAP_KILL) check

The CAP_KILL check in exit_notify() looks just wrong, kill it.

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

Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Serge Hallyn <[email protected]>

--- 6.30/kernel/exit.c~EXIT_CAP_KILL 2009-04-06 00:03:42.000000000 +0200
+++ 6.30/kernel/exit.c 2009-04-06 15:30:32.000000000 +0200
@@ -837,8 +837,7 @@ 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);

2009-04-06 19:38:21

by Roland McGrath

Subject: Re: [PATCH, RESEND] exit_notify: kill the wrong capable(CAP_KILL) check

Acked-by: Roland McGrath <[email protected]>