linux-hardening - Re: [PATCH 1/2] fs/exec: Explicitly unshare fs

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Date:   Thu, 13 Oct 2022 20:54:14 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Jann Horn <jannh@...gle.com>,
        Christian Brauner <brauner@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Jorge Merlino <jorge.merlino@...onical.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        John Johansen <john.johansen@...onical.com>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Richard Haines <richard_c_haines@...nternet.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Todd Kjos <tkjos@...gle.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Prashanth Prahlad <pprahlad@...hat.com>,
        Micah Morton <mortonm@...omium.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Andrei Vagin <avagin@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org,
        selinux@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/2] fs/exec: Explicitly unshare fs_struct on exec

On Thu, Oct 13, 2022 at 08:18:04PM -0700, Andy Lutomirski wrote:
> But seriously, this makes no sense at all.  It should not be possible to exec a program and then, without ptrace, change its cwd out from under it.  Do we really need to preserve this behavior?

Yup, already abandoned:
https://lore.kernel.org/lkml/202210061301.207A20C8E5@keescook/

-- 
Kees Cook