linux-kernel - Re: SECCOMP_IOCTL_NOTIF

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Message-ID: <20201201124105.GB103125@cisco>
Date:   Tue, 1 Dec 2020 07:41:05 -0500
From:   Tycho Andersen <tycho@...ho.pizza>
To:     Alban Crequy <alban@...volk.io>
Cc:     Giuseppe Scrivano <gscrivan@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: SECCOMP_IOCTL_NOTIF_ADDFD race condition

On Mon, Nov 30, 2020 at 06:20:09PM -0500, Tycho Andersen wrote:
> Idea 1 sounds best to me, but maybe that's because it's the way I
> originally did the fd support that never landed :)
> 
> But here's an Idea 4: we add a way to remotely close an fd (I don't
> see that the current infra can do this, but perhaps I didn't look hard
> enough), and then when you get ENOENT you have to close the fd. Of
> course, this can't be via seccomp, so maybe it's even more racy.

Or better yet: what if the kernel closed everything it had added via
ADDFD if it didn't get a valid response from the supervisor? Then
everyone gets this bug fixed for free.

Tycho