[PATCH] connector: Fix sid connector (was: Badness at kernel/softirq.c:143...)

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am Dienstag 29 September 2009 15:24:15 schrieb Oleg Nesterov:
> On 09/29, Evgeny Polyakov wrote:
> > I'm yet do download the latest git to check this particular patch, but
> > I suppose it is possible to copy data under the lock into temporary
> > buffer and then send it using existing infrastructure instead of
> > calling it under the tasklist lock.
> 
> Afaics, we can just shift proc_sid_connector() from __set_special_pids()
> to sys_setsid().

Ok,  can confirm that this patch fixes my problem, but I am not sure if the
intended behaviour is still working as expected.

[PATCH] connector: Fix sid connector

The sid connector gives the following warning:
Badness at kernel/softirq.c:143
[...]
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. We can safely move proc_sid_connector from
__set_special_pids to sys_setsid.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

---
 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)
+		proc_sid_connector(sid);
 	return err;
 }