From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH] connector: Fix regression introduced by sid connector Date: Fri, 2 Oct 2009 08:16:41 +0200 Message-ID: <200910020816.41323.borntraeger@de.ibm.com> References: <200909251123.03482.borntraeger@de.ibm.com> <200909300843.11208.borntraeger@de.ibm.com> <20091001141426.2c1a0139.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: oleg@redhat.com, scott@ubuntu.com, zbr@ioremap.net, linux-kernel@vger.kernel.org, matthltc@us.ibm.com, davem@davemloft.net, netdev@vger.kernel.org To: Andrew Morton Return-path: In-Reply-To: <20091001141426.2c1a0139.akpm@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Sorry about that. Dont know how this escaped. It was probably hiding between all the sparse warnings I get in kernel/* and a lack of knowledge in this area. Here is a new version: since commit 02b51df1b07b4e9ca823c89284e704cadb323cd1 (proc connector: add event for process becoming session leader) we have the following warning: Badness at kernel/softirq.c:143 [...] Krnl PSW : 0404c00180000000 00000000001481d4 (local_bh_enable+0xb0/0xe0) [...] Call Trace: ([<000000013fe04100>] 0x13fe04100) [<000000000048a946>] sk_filter+0x9a/0xd0 [<000000000049d938>] netlink_broadcast+0x2c0/0x53c [<00000000003ba9ae>] cn_netlink_send+0x272/0x2b0 [<00000000003baef0>] proc_sid_connector+0xc4/0xd4 [<0000000000142604>] __set_special_pids+0x58/0x90 [<0000000000159938>] sys_setsid+0xb4/0xd8 [<00000000001187fe>] sysc_noemu+0x10/0x16 [<00000041616cb266>] 0x41616cb266 The warning is ---> WARN_ON_ONCE(in_irq() || irqs_disabled()); The network code must not be called with disabled interrupts but sys_setsid holds the tasklist_lock with spinlock_irq while calling the connector. After a discussion we agreed that we can move proc_sid_connector from __set_special_pids to sys_setsid. We also agreed that it is sufficient to change the check from task_session(curr) != pid into err > 0, since if we don't change the session, this means we were already the leader and return -EPERM. One last thing: There is also daemonize(), and some people might want to get a notification in that case. Since daemonize() is only needed if a user space does kernel_thread this does not look important (and there seems to be no consensus if this connector should be called in daemonize). If we really want this, we can add proc_sid_connector to daemonize() in an additional patch (Scott?) Signed-off-by: Christian Borntraeger CCed: Scott James Remnant CCed: Matt Helsley CCed: David S. Miller Acked-by: Oleg Nesterov Acked-by: Evgeniy Polyakov --- kernel/exit.c | 4 +--- kernel/sys.c | 2 ++ 2 files changed, 3 insertions(+), 3 deletions(-) Index: linux-2.6/kernel/exit.c =================================================================== --- linux-2.6.orig/kernel/exit.c +++ linux-2.6/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); Index: linux-2.6/kernel/sys.c =================================================================== --- linux-2.6.orig/kernel/sys.c +++ linux-2.6/kernel/sys.c @@ -1110,6 +1110,8 @@ SYSCALL_DEFINE0(setsid) err = session; out: write_unlock_irq(&tasklist_lock); + if (err > 0) + proc_sid_connector(group_leader); return err; }