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:     Andy Lutomirski <luto@amacapital.net>
Cc:     David Howells <dhowells@redhat.com>, viro@zeniv.linux.org.uk,
        John Johansen <john.johansen@canonical.com>,
        Tejun Heo <tj@kernel.org>, selinux@tycho.nsa.gov,
        Paul Moore <paul@paul-moore.com>,
        Li Zefan <lizefan@huawei.com>, linux-api@vger.kernel.org,
        apparmor@lists.ubuntu.com,
        Casey Schaufler <casey@schaufler-ca.com>, fenghua.yu@intel.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Eric Biggers <ebiggers@google.com>,
        linux-security-module@vger.kernel.org,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        tomoyo-dev-en@lists.sourceforge.jp, cgroups@vger.kernel.org,
        torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, "Theodore Y. Ts'o" <tytso@mit.edu>,
        Miklos Szeredi <miklos@szeredi.hu>
References: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk>
        <87d0uqpba5.fsf@xmission.com>
        <0F2FA70F-8C7E-4D7D-B685-244A76BDB459@amacapital.net>
Date:   Fri, 10 Aug 2018 10:17:37 -0500
In-Reply-To: <0F2FA70F-8C7E-4D7D-B685-244A76BDB459@amacapital.net> (Andy
        Lutomirski's message of "Fri, 10 Aug 2018 07:36:17 -0700")
Message-ID: <8736vmp7xq.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: BUG: Mount ignores mount options
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Andy Lutomirski <luto@amacapital.net> writes:

>> On Aug 10, 2018, at 7:05 AM, Eric W. Biederman <ebiederm@xmission.com> wrote:
>> 
>> 
>> There is a serious problem with mount options today that fsopen does not
>> address.  The problem is that mount options are ignored for block based
>> filesystems, and any other type of filesystem that follows the same
>> pattern.
>> 
>
>> /dev/loop0 /root/loop0-noacl-noquota-nouser_xattr ext4 rw,relatime,nouser_xattr,noacl 0 0
>> /dev/loop0 /root/loop0-acl-quota-user_xattr ext4 rw,relatime,nouser_xattr,noacl 0 0
>
> To make sure I understand correctly: the problem is that the second
> mount ignored the options because the device was already mounted,
> right?

Yes.

> For the new API, I think the only remotely sane approach is to refuse
> to mount or init or whatever you call it an already mounted bdev. If
> user code genuinely needs to bind-mount an existing mount that is
> known only by its bdev, we can add a specific API just for that.

Eric