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Date: Tue, 1 Dec 2009 20:53:00 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       Christoph Hellwig <hch@infradead.org>, Nick Piggin <npiggin@suse.de>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Al Viro <viro@zeniv.linux.org.uk>, James Morris <jmorris@namei.org>
Subject: Re: [PATCH] audit: Call tty_audit_push_task() outside preempt disabled
 region
In-Reply-To: <20091201182202.GA12754@redhat.com>
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On Tue, 1 Dec 2009, Oleg Nesterov wrote:
> On 12/01, Thomas Gleixner wrote:
> >
> > -void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
> > +int tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
> >  {
> > -	struct tty_audit_buf *buf;
> > +	struct tty_audit_buf *buf = NULL;
> > +	unsigned long flags;
> >
> > -	spin_lock_irq(&tsk->sighand->siglock);
> > -	buf = tsk->signal->tty_audit_buf;
> > -	if (buf)
> > +	if (!lock_task_sighand(tsk, &flags))
> > +		return -ESRCH;
> > +
> > +	if (tsk->signal->audit_tty && tsk->signal->tty_audit_buf) {
> > +		buf = tsk->signal->tty_audit_buf;
> >  		atomic_inc(&buf->count);
> > -	spin_unlock_irq(&tsk->sighand->siglock);
> > +	}
> > +	unlock_task_sighand(tsk, &flags);
> > +
> >  	if (!buf)
> > -		return;
> > +		return -EPERM;
> 
> I think the patch is correct, but it changes the behaviour of
> audit_prepare_user_tty() a bit.
> 
> Suppose that signal->audit_tty != NULL but signal->tty_audit_buf
> is not allocated yet. In this audit_prepare_user_tty() returns 0
> before the patch and -EPERM after.
> 
> I do not know if this matters, just to be sure this is OK.

Hmm, true. Missed that. Thanks for catching it.

     tglx