linux-kernel - Re: [RESEND][RFC PATCH v2] waitfd

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: <20090108143220.GA8717@redhat.com>
Date:	Thu, 8 Jan 2009 15:32:20 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ulrich Drepper <drepper@...il.com>
Cc:	Roland McGrath <roland@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Casey Dahlin <cdahlin@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RESEND][RFC PATCH v2] waitfd

On 01/07, Ulrich Drepper wrote:
>
> On Wed, Jan 7, 2009 at 12:53 PM, Roland McGrath <roland@...hat.com> wrote:
> > Do we really need another one for this?  How about using signalfd plus
> > setting the child's exit_signal to a queuing (SIGRTMIN+n) signal instead of
> > SIGCHLD?  It's slightly more magical for the userland process to know to do
> > that (fork -> clone SIGRTMIN).  But compared to adding a syscall we don't
> > really have to add, maybe better.
>
> Since waitfd shouldn't consume the child termination notification
> waitfd should be more widely usable than the wait*() interfaces.

yes, it doesn't eat the notification (SIGCHLD), but it reaps a
zombie, clears ->exit_code TASK_STOPPED/TASK_TRACED tasks, clears
SIGNAL_STOP_CONTINUED.

> I.e., it's not necessary to restrict the use to parents.  Any process
> with the same UID should be allowed to call waitfd.  This would allow
> some new user cases.

I don't see how it is possible to implement this...

The parent can sleep on ->wait_chldexit and it will be notified, but
how can we wait for the unrelated process with the same UID ?

Even if sys_waitfd() uses P_PID, we can't use task->parent->signal->wait_chldexit,
task->parent can exit before task exits.


Or I misunderstood you?

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/