From patchwork Tue Sep 29 14:07:18 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evgeniy Polyakov X-Patchwork-Id: 34431 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by ozlabs.org (Postfix) with ESMTP id A89011007D1 for ; Wed, 30 Sep 2009 00:08:11 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752507AbZI2OHR (ORCPT ); Tue, 29 Sep 2009 10:07:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751585AbZI2OHR (ORCPT ); Tue, 29 Sep 2009 10:07:17 -0400 Received: from netgear.net.ru ([195.178.208.66]:33817 "EHLO tservice.net.ru" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751343AbZI2OHQ (ORCPT ); Tue, 29 Sep 2009 10:07:16 -0400 Received: by tservice.net.ru (Postfix, from userid 1000) id 136F0100C7; Tue, 29 Sep 2009 18:07:18 +0400 (MSD) Date: Tue, 29 Sep 2009 18:07:18 +0400 From: Evgeniy Polyakov To: Christian Borntraeger Cc: Oleg Nesterov , Evgeny Polyakov , Scott James Remnant , Linux Kernel , Matt Helsley , "David S. Miller" , netdev@vger.kernel.org Subject: Re: [PATCH] connector: Fix sid connector (was: Badness at kernel/softirq.c:143...) Message-ID: <20090929140718.GA23858@ioremap.net> References: <200909251123.03482.borntraeger@de.ibm.com> <20090929132415.GB4538@redhat.com> <200909291547.21528.borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <200909291547.21528.borntraeger@de.ibm.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Sep 29, 2009 at 03:47:21PM +0200, Christian Borntraeger (borntraeger@de.ibm.com) wrote: > Ok, can confirm that this patch fixes my problem, but I am not sure if the > intended behaviour is still working as expected. Your patch breaks assumption that task_session(current->group_leader) is not equal to new session id, but to check task_session() we need either rcu or task lock. Also setsid() return value is not zero or negative error, but new session ID or negative error, so I believe attached patch is a proper fix, although it looks rather ugly. Also proc_sid_connector() uses GFP_KERNEL allocation which is way too wrong to use under any locks. Something like this (not tested :) diff --git a/kernel/exit.c b/kernel/exit.c index 5859f59..1565baf 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -359,10 +359,8 @@ void __set_special_pids(struct pid *pid) { struct task_struct *curr = current->group_leader; - if (task_session(curr) != pid) { + if (task_session(curr) != pid) change_pid(curr, PIDTYPE_SID, pid); - proc_sid_connector(curr); - } if (task_pgrp(curr) != pid) change_pid(curr, PIDTYPE_PGID, pid); diff --git a/kernel/sys.c b/kernel/sys.c index 255475d..b852a8b 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1090,6 +1090,7 @@ SYSCALL_DEFINE0(setsid) struct pid *sid = task_pid(group_leader); pid_t session = pid_vnr(sid); int err = -EPERM; + int send_cn = 0; write_lock_irq(&tasklist_lock); /* Fail if I am already a session leader */ @@ -1104,12 +1105,18 @@ SYSCALL_DEFINE0(setsid) group_leader->signal->leader = 1; __set_special_pids(sid); + if (task_session(group_leader) != sid) + send_cn = 1; proc_clear_tty(group_leader); err = session; out: write_unlock_irq(&tasklist_lock); + + if (send_cn) + proc_sid_connector(group_leader); + return err; }