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

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Date:	Tue, 29 Sep 2009 16:25:38 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	Christian Borntraeger <borntraeger@...ibm.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 09/29, Evgeniy Polyakov wrote:
>
> 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,

Afaics, no.

> --- 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;

This is not right, task_session(group_leader) must be == sid after
__set_special_pids().

And I don't think "int send_cn" is needed. sys_setsid() must not
succeed if the caller lived in session == task_pid(group_leader).

Or I missed your point?

Oleg.

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