linux-kernel - Re: [PATCH v5 1/1] fs: Allow no_new

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Date:   Wed, 31 Mar 2021 06:33:02 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Kees Cook <keescook@...omium.org>
Cc:     Casey Schaufler <casey@...aufler-ca.com>,
        Mickaël Salaün <mic@...ikod.net>,
        James Morris <jmorris@...ei.org>,
        Serge Hallyn <serge@...lyn.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christoph Hellwig <hch@....de>,
        David Howells <dhowells@...hat.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Jann Horn <jannh@...gle.com>,
        John Johansen <john.johansen@...onical.com>,
        Kentaro Takeda <takedakn@...data.co.jp>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        kernel-hardening@...ts.openwall.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v5 1/1] fs: Allow no_new_privs tasks to call chroot(2)

On Tue, Mar 30, 2021 at 11:03:10PM -0700, Kees Cook wrote:

> Regardless, I still endorse this change because it doesn't make things
> _worse_, since without this, a compromised process wouldn't need ANY
> tricks to escape a chroot because it wouldn't be in one. :) It'd be nice
> if there were some way to make future openat() calls be unable to
> resolve outside the chroot, but I view that as an enhancement.
> 
> But, as it stands, I think this makes sense and I stand by my
> Reviewed-by tag. If Al is too busy to take it, and James would rather
> not take VFS, perhaps akpm would carry it? That's where other similar
> VFS security work has landed.

Frankly, I'm less than fond of that thing, but right now I'm buried
under all kinds of crap (->d_revalidate() joy, mostly).  I'll post
a review, but for now it's very definitely does *not* get an implicit
ACK from me.