Re: [PATCH] connector: Fix sid connector (was: Badness at kernel/softirq.c:143...)
From: Evgeniy Polyakov <hidden>
Date: 2009-09-29 14:07:18
Also in:
lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
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; }
--
Evgeniy Polyakov