linux-kernel - RE: [PATCH v2 1/1] fs: Allow no_new

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Date:   Thu, 11 Mar 2021 09:45:43 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Eric W. Biederman'" <ebiederm@...ssion.com>,
        Mickaël Salaün <mic@...ikod.net>
CC:     Al Viro <viro@...iv.linux.org.uk>,
        James Morris <jmorris@...ei.org>,
        Serge Hallyn <serge@...lyn.com>,
        Andy Lutomirski <luto@...capital.net>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christoph Hellwig <hch@....de>,
        David Howells <dhowells@...hat.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        "John Johansen" <john.johansen@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        Kentaro Takeda <takedakn@...data.co.jp>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: RE: [PATCH v2 1/1] fs: Allow no_new_privs tasks to call chroot(2)

From: Eric W. Biederman
> Sent: 10 March 2021 19:24
...
> The actual classic chroot escape is.
> chdir("/");
> chroot("/somedir");
> chdir("../../../..");

That one is easily checked.

I thought something like:
chroot("/somedir");
chdir("/somepath");

Friendly process:
mvdir("/somedir/some_path", "/bar");

was the actual escape?

	David

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