linux-kernel - Re: [PATCH RFC v2 1/2] selinux: Fix selinux_sb_mnt_opts

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Date:   Tue, 1 Feb 2022 15:38:16 +0100
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Scott Mayhew <smayhew@...hat.com>,
        SElinux list <selinux@...r.kernel.org>,
        linux-nfs <linux-nfs@...r.kernel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 1/2] selinux: Fix selinux_sb_mnt_opts_compat()

On Mon, Jan 31, 2022 at 5:16 PM Paul Moore <paul@...l-moore.com> wrote:
> On Mon, Jan 31, 2022 at 7:46 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> > On Fri, Jan 28, 2022 at 3:28 AM Paul Moore <paul@...l-moore.com> wrote:
> > > On Thu, Jan 27, 2022 at 4:54 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> > > > I wonder if we could make this all much simpler by *always* doing the
> > > > label parsing in selinux_add_opt() and just returning an error when
> > > > !selinux_initialized(&selinux_state). Before the new mount API, mount
> > > > options were always passed directly to the mount(2) syscall, so it
> > > > wasn't possible to pass any SELinux mount options before the SELinux
> > > > policy was loaded. I don't see why we need to jump through hoops here
> > > > just to support this pseudo-feature of stashing an unparsed label into
> > > > an fs_context before policy is loaded... Userspace should never need
> > > > to do that.
> > >
> > > I could agree with that, although part of my mind is a little nervous
> > > about the "userspace should *never* ..." because that always seems to
> > > bite us.  Although I'm struggling to think of a case where userspace
> > > would need to set explicit SELinux mount options without having a
> > > policy loaded.
> >
> > I get that, but IMO this is enough of an odd "use case" that I
> > wouldn't worry too much ...
>
> I understand, but seeing as I'm the only one that defends these things
> with Linus and others lets do this:

It's not all black and white:
https://lore.kernel.org/lkml/Pine.LNX.4.64.0512291322560.3298@g5.osdl.org/

> 1. Fix what we have now using Scott's patches once he incorporates the feedback.
> 2. Merge another patch (separate patch(set) please!) which does the
> parsing in selinux_add_opt().
>
> ... this was if we have to revert #2 we still have the fixes in #1.

Sounds good to me. I can prepare the simplification patch. If anyone
does come to complain, then by all means, let's revert it.

--
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.