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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     David Howells <dhowells@redhat.com>
Cc:     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: <87d0uqpba5.fsf@xmission.com>
        <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk>
        <22361.1533913891@warthog.procyon.org.uk>
Date:   Fri, 10 Aug 2018 20:19:25 -0500
In-Reply-To: <22361.1533913891@warthog.procyon.org.uk> (David Howells's
        message of "Fri, 10 Aug 2018 16:11:31 +0100")
Message-ID: <87pnyphf8i.fsf@xmission.com>
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Subject: Re: BUG: Mount ignores mount options
Sender: linux-kernel-owner@vger.kernel.org
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David Howells <dhowells@redhat.com> writes:

> 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.
>
> Yes.  Since you *absolutely* *insist* on this being fixed *right* *now* *or*
> *else*, I'm working up a set of additional patches to give userspace the
> option of whether they want no sharing; sharing, but only with exactly the
> same parameters; or to ignore the parameter differences and just accept
> sharing of what's already already mounted (ie. the current behaviour).
>
> The second option, however, is not trivial as it needs to compare the fs
> contexts, including the LSM parameters.  To make that work, I really need to
> remove the old security_mnt_opts stuff - which means I need to port btrfs to
> the new context stuff.
>
> We discussed this yesterday, and I proposed a solution, and I'm working on it.

I repeated this because after some comments from Al on IRC yesterday
and Miklos's email replay. It appeared clear that I had not specified
why my issue was clearly enough for people reading the thread to
understand the problem that I see.

> Yes, I agree it would be nice to have, but it *doesn't* really need supporting
> right this minute, since what I have now oughtn't to break the current
> behaviour.

I am really reluctant to endorse anything that propagates the issues of
the current interface in the new mount interface.

Eric