Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Miklos Szeredi <mszeredi@redhat.com>
Cc:     lkml <linux-kernel@vger.kernel.org>,
        Linux Containers <containers@lists.linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Alban Crequy <alban@kinvolk.io>,
        Seth Forshee <seth.forshee@canonical.com>,
        Sargun Dhillon <sargun@sargun.me>,
        Dongsu Park <dongsu@kinvolk.io>,
        "Serge E. Hallyn" <serge@hallyn.com>
References: <878tbmf5vl.fsf@xmission.com>
        <20180221202908.17258-4-ebiederm@xmission.com>
        <CAOssrKeNLBeMkMrrCeRBO9Z80zFxCCEygKL3DErnQ9xBoLkH0g@mail.gmail.com>
Date:   Thu, 22 Feb 2018 13:18:33 -0600
In-Reply-To: <CAOssrKeNLBeMkMrrCeRBO9Z80zFxCCEygKL3DErnQ9xBoLkH0g@mail.gmail.com>
        (Miklos Szeredi's message of "Thu, 22 Feb 2018 12:40:18 +0100")
Message-ID: <87inao6dfa.fsf@xmission.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [PATCH v6 4/5] fuse: Ensure posix acls are translated outside of init_user_ns
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Miklos Szeredi <mszeredi@redhat.com> writes:

> On Wed, Feb 21, 2018 at 9:29 PM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>> Ensure the translation happens by failing to read or write
>> posix acls when the filesystem has not indicated it supports
>> posix acls.
>
> For the first iteration this is fine, but  we could convert the raw
> xattrs as well, if we later want to, right?

I will say maybe.  This is tricky.   The code would not be too hard,
and the function to do the work posix_acl_fix_xattr_userns already
exists in fs/posix_acl.c

I don't actually expect that to work longterm.  I expect the direction
the kernel internals are moving is that all filesystems that implement
posix acls will be expected to implement .get_acl and .set_acl.

I would have to reread the old thread that got us to this point with
posix acls before I could really understand the backwards compatible
fuse use case, and I would have to reread the rest of the acl processing
in the kernel before I could recall exactly what makes sense.

If there was an obvious way to whitelist xattrs that fuse can support
for user namespaces I think I would go for that.  Just to avoid future
problems with future xattrs.

Eric