linux-kernel - Re: [PATCH] tty: fix leakage of -ERESTARTSYS to userland

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Date:	Wed, 30 May 2007 23:18:49 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: fix leakage of -ERESTARTSYS to userland

On 05/30, Andrew Morton wrote:
> On Tue, 29 May 2007 22:44:35 +0400
> Oleg Nesterov <oleg@...sign.ru> wrote:
> 
> > --- t/drivers/char/n_tty.c~	2007-04-05 12:18:26.000000000 +0400
> > +++ t/drivers/char/n_tty.c	2007-05-28 10:57:58.000000000 +0400
> > @@ -1191,6 +1191,7 @@ static int job_control(struct tty_struct
> >  			    is_current_pgrp_orphaned())
> >  				return -EIO;
> >  			kill_pgrp(task_pgrp(current), SIGTTIN, 1);
> > +			set_thread_flag(TIF_SIGPENDING);
> >  			return -ERESTARTSYS;
> >  		}
> >  	}
> 
> Are there other callers of kill_pgrp() which have the same problem?

Hopefully no.

> Perhaps we should have a kill_pgrp_self() which takes care of doing
> this, rather than open-coding it.  Something with a comment which
> explains what's going on ;)

This set_thread_flag(TIF_SIGPENDING) is "connected" to "return -ERESTARTSYS",
not to kill_pgrp(), imho the new helper is not so suitable.

Perhaps it makes sense to add the comment into include/linux/errno.h, to
explain that -ERESTART... codes are only valid when signal_pending() == true.

Oleg.

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