linux-kernel - Re: [PATCH] Use ERESTARTNOHAND if poll() is interrupted by a signal

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070731001847.GA623@tv-sign.ru>
Date:	Tue, 31 Jul 2007 04:18:47 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Manfred Spraul <manfred@...orfullife.com>,
	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH] Use ERESTARTNOHAND if poll() is interrupted by a signal

On 07/31, Oleg Nesterov wrote:
>
> > Manfred Spraul <manfred@...orfullife.com> wrote:
> > 
> > > poll() returns -EINTR if a signal is pending.
> > > EINTR is a bad choice: it means that poll returns to user space if the
> > > task is stopped by SIGSTOP/SIGCONT or by the freezer.
> > > select() and ppoll() both use ERESTARTNOHAND, this avoids a return to
> > > user space for signals that are handled by the kernel.
> > > 
> > > The patch switches poll() to ERESTARTNOHAND.
> > > Tested with FC6. Patch against 2.6.23-rc1-mm1.
> > 
> > > --- 2.6/fs/select.c	2007-07-28 20:31:51.000000000 +0200
> > > +++ build-2.6/fs/select.c	2007-07-28 21:21:52.000000000 +0200
> > > @@ -621,7 +621,7 @@ static int do_poll(unsigned int nfds,  s
> > >  		if (!count) {
> > >  			count = wait->error;
> > >  			if (signal_pending(current))
> > > -				count = -EINTR;
> > > +				count = -ERESTARTNOHAND;
> 
> I am not sure. This means we restart sys_poll() with the same timeout
> if there is no pending signal. I think we need ERESTART_RESTARTBLOCK
> logic.

Forgot to mention, sys_select() can use ERESTARTNOHAND because it
modifies "struct timeval __user *tvp" before return, but sys_poll()
gets timeout_msecs by value.

Oleg.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/