linux-kernel - Re: [PATCH v2 0/7] CLONE_FD: Task exit notification via file descriptor

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Message-ID: <CAGXu5j+rCaWke5ajy3Lb4jWs+o_P-XidBCMGNqg7w5sVwbDRxA@mail.gmail.com>
Date:	Mon, 16 Mar 2015 16:26:12 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Thiago Macieira <thiago.macieira@...el.com>
Cc:	Josh Triplett <josh@...htriplett.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rik van Riel <riel@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v2 0/7] CLONE_FD: Task exit notification via file descriptor

On Mon, Mar 16, 2015 at 3:50 PM, Thiago Macieira
<thiago.macieira@...el.com> wrote:
> On Monday 16 March 2015 15:36:16 Kees Cook wrote:
>> And just so I understand the races here, what happens in CLONE_FD
>> (without CLONE_AUTOREAP) case where the child dies, but the parent
>> never reads from the CLONE_FD fd, and closes it (or dies)? Will the
>> modes switch that late in the child's lifetime? (i.e. even though the
>> details were written to the fd, they were never read, yet it'll still
>> switch and generate a SIGCHLD, etc?)
>
> What happens to a child that dies during the parent's lifetime but the parent
> exits without reaping the child?
>
> The same should happen, whatever that behaviour is.

Okay, sounds like the waitpid internals are tied to the read, not the
child death. Perfect, that means it'll still be waitpid-able by
whatever process inherits the zombie. Sounds good! Thanks for
clarifying. :)

-Kees

-- 
Kees Cook
Chrome OS Security
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