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

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Message-ID: <d2a6ccdd8a734d36ae88866a4c16019b@AcuMS.aculab.com>
Date:   Fri, 14 Oct 2022 22:03:18 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andy Lutomirski' <luto@...nel.org>, Jann Horn <jannh@...gle.com>,
        Christian Brauner <brauner@...nel.org>
CC:     Kees Cook <keescook@...omium.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-mm@...ck.org>,
        "linux-fsdevel@...r.kernel.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" <apparmor@...ts.ubuntu.com>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: RE: [PATCH 1/2] fs/exec: Explicitly unshare fs_struct on exec

From: Andy Lutomirski
> Sent: 14 October 2022 04:18
...
> 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?

it maybe ok if the exec'ed program also 'bought-in' to the
fact that its cwd and open files might get changed.
But imagine someone doing it to a login shell!

	David

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