linux-ext4 - Re: [PATCH v6 16/40] open: handle idmapped mounts

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Message-ID: <f99675af-c1-8a1a-34ef-1f701b5e9ec@namei.org>
Date:   Fri, 22 Jan 2021 15:14:30 +1100 (AEDT)
From:   James Morris <jmorris@...ei.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, linux-fsdevel@...r.kernel.org,
        John Johansen <john.johansen@...onical.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Geoffrey Thomas <geofft@...reload.com>,
        Mrunal Patel <mpatel@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        Andy Lutomirski <luto@...nel.org>,
        Theodore Tso <tytso@....edu>, Alban Crequy <alban@...volk.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Howells <dhowells@...hat.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Lennart Poettering <lennart@...ttering.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>, smbarber@...omium.org,
        Phil Estes <estesp@...il.com>, Serge Hallyn <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>,
        Todd Kjos <tkjos@...gle.com>, Paul Moore <paul@...l-moore.com>,
        Jonathan Corbet <corbet@....net>,
        containers@...ts.linux-foundation.org,
        linux-security-module@...r.kernel.org, linux-api@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-integrity@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v6 16/40] open: handle idmapped mounts

On Thu, 21 Jan 2021, Christian Brauner wrote:

> For core file operations such as changing directories or chrooting,
> determining file access, changing mode or ownership the vfs will verify
> that the caller is privileged over the inode. Extend the various helpers
> to handle idmapped mounts. If the inode is accessed through an idmapped
> mount map it into the mount's user namespace. Afterwards the permissions
> checks are identical to non-idmapped mounts. When changing file
> ownership we need to map the uid and gid from the mount's user
> namespace. If the initial user namespace is passed nothing changes so
> non-idmapped mounts will see identical behavior as before.
> 
> Link: https://lore.kernel.org/r/20210112220124.837960-24-christian.brauner@ubuntu.com
> Cc: Christoph Hellwig <hch@....de>
> Cc: David Howells <dhowells@...hat.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: linux-fsdevel@...r.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>


Reviewed-by: James Morris <jamorris@...ux.microsoft.com>


-- 
James Morris
<jmorris@...ei.org>