Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932564Ab2EDUrG (ORCPT ); Fri, 4 May 2012 16:47:06 -0400 Received: from mail-pz0-f45.google.com ([209.85.210.45]:45099 "EHLO mail-pz0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932434Ab2EDUq7 (ORCPT ); Fri, 4 May 2012 16:46:59 -0400 Message-Id: <20120504204229.329386059@linuxfoundation.org> User-Agent: quilt/0.60-19.1 Date: Fri, 04 May 2012 13:43:22 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov Subject: [ 58/75] exit_signal: fix the "parent has changed security domain" logic In-Reply-To: <20120504204258.GA12552@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2529 Lines: 78 3.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov commit b6e238dceed36891cc633167afe7151f1f3d83c5 upstream. exit_notify() changes ->exit_signal if the parent already did exec. This doesn't really work, we are not going to send the signal now if there is another live thread or the exiting task is traced. The parent can exec before the last dies or the tracer detaches. Move this check into do_notify_parent() which actually sends the signal. The user-visible change is that we do not change ->exit_signal, and thus the exiting task is still "clone children" for do_wait()->eligible_child(__WCLONE). Hopefully this is fine, the current logic is racy anyway. Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/exit.c | 14 -------------- kernel/signal.c | 9 +++++++++ 2 files changed, 9 insertions(+), 14 deletions(-) --- a/kernel/exit.c +++ b/kernel/exit.c @@ -818,20 +818,6 @@ static void exit_notify(struct task_stru if (group_dead) kill_orphaned_pgrp(tsk->group_leader, NULL); - /* Let father know we died - * - * Thread signals are configurable, but you aren't going to use - * that to send signals to arbitrary processes. - * That stops right now. - * - * If the parent exec id doesn't match the exec id we saved - * when we started then we know the parent has changed security - * domain. - */ - if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD && - tsk->parent_exec_id != tsk->real_parent->self_exec_id) - tsk->exit_signal = SIGCHLD; - if (unlikely(tsk->ptrace)) { int sig = thread_group_leader(tsk) && thread_group_empty(tsk) && --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1642,6 +1642,15 @@ bool do_notify_parent(struct task_struct BUG_ON(!tsk->ptrace && (tsk->group_leader != tsk || !thread_group_empty(tsk))); + if (sig != SIGCHLD) { + /* + * This is only possible if parent == real_parent. + * Check if it has changed security domain. + */ + if (tsk->parent_exec_id != tsk->parent->self_exec_id) + sig = SIGCHLD; + } + info.si_signo = sig; info.si_errno = 0; /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/