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Message-ID: <20090929140718.GA23858@ioremap.net>
Date: Tue, 29 Sep 2009 18:07:18 +0400
From: Evgeniy Polyakov <zbr@...emap.net>
To: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Oleg Nesterov <oleg@...hat.com>,
Evgeny Polyakov <johnpol@....mipt.ru>,
Scott James Remnant <scott@...ntu.com>,
Linux Kernel <linux-kernel@...r.kernel.org>,
Matt Helsley <matthltc@...ibm.com>,
"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] connector: Fix sid connector (was: Badness at kernel/softirq.c:143...)
On Tue, Sep 29, 2009 at 03:47:21PM +0200, Christian Borntraeger (borntraeger@...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
--
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