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Date: Sun, 11 Mar 2012 18:49:53 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Djalal Harouni <tixxdz@...ndz.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
Andrew Morton <akpm@...ux-foundation.org>,
Al Viro <viro@...iv.linux.org.uk>,
Alexey Dobriyan <adobriyan@...il.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Vasiliy Kulikov <segoon@...nwall.com>,
Kees Cook <keescook@...omium.org>, Solar Designer <solar@...nwall.com>,
WANG Cong <xiyou.wangcong@...il.com>,
James Morris <james.l.morris@...cle.com>,
linux-security-module@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Greg KH <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...e.hu>,
Stephen Wilson <wilsons@...rt.ca>,
"Jason A. Donenfeld" <Jason@...c4.com>
Subject: self_exec_id/parent_exec_id && CLONE_PARENT
(change subject)
On 03/11, Oleg Nesterov wrote:
>
> Well, I don't think it is right to add this counter into task_struct.
>
> It should be per-process, signal_struct makes more sense. Or may be
> mm_struct.
>
> Btw this is also true for parent_exec_id/self_exec_id, but this is
> another story.
In fact I think it would be nice to kill parent_exec_id/self_exec_id.
Afaics, this only problem is clone(CLONE_PARENT | SIGXXX). I expect
the answer is "no, can break existing applications", but I'll ask
anyway.
Can't we change this? IOW, can't we modify copy_process
- p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
+ p->exit_signal =
+ (clone_flags & CLONE_THREAD) ? -1 :
+ (clobe_flags & CLONE_PARENT) ? current->group_leader->exit_signal :
+ (clone_flags & CSIGNAL);
(or simply use SIGCHLD instead of group_leader->exit_signal).
Then we can kill parent_exec_id/self_exec_id if me modify de_thread()
to set ->exit_signal = SIGCHLD for every child.
I am also asking because the change above looks like the fix to me.
The child must not control its ->exit_signal, it is the parent who
decides which signal the child should use for notification.
And to me, clone(CLONE_PARENT | SIGXXX) looks like a violation of
rule above.
Oleg.
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