Re: [PATCH 0/2] vfs/security/NFS/btrfs: clean up and fix LSM option handling

From: Ondrej Mosnacek <omosnace@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linux Security Module list 
	<linux-security-module@vger.kernel.org>,
	SElinux list <selinux@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-nfs <linux-nfs@vger.kernel.org>,
	linux-btrfs@vger.kernel.org, Paul Moore <paul@paul-moore.com>,
	Olga Kornievskaia <aglo@umich.edu>,
	David Howells <dhowells@redhat.com>,
	Stephen Smalley <stephen.smalley.work@gmail.com>
Subject: Re: [PATCH 0/2] vfs/security/NFS/btrfs: clean up and fix LSM option handling
Date: Mon, 17 May 2021 15:46:04 +0200	[thread overview]
Message-ID: <CAFqZXNs6dVkAj4GYme1-COU-EvmTxRXAgS6oTUQpxxjNiamyzg@mail.gmail.com> (raw)
In-Reply-To: <CAFqZXNuhog5YfaG9CBVmZ+C3mSzAEgZkSC-mrQGOD4vyLEz4Xw@mail.gmail.com>

On Fri, Apr 9, 2021 at 7:39 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> On Fri, Apr 9, 2021 at 2:28 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > On Fri, Apr 09, 2021 at 01:12:52PM +0200, Ondrej Mosnacek wrote:
> > > This series attempts to clean up part of the mess that has grown around
> > > the LSM mount option handling across different subsystems.
> >
> > I would not describe growing another FS_... flag
>
> Why is that necessarily a bad thing?
>
> > *AND* spreading the
> > FS_BINARY_MOUNTDATA further, with rather weird semantics at that,
> > as a cleanup of any sort.
>
> How is this spreading it further? The patches remove one (rather bad)
> use of it in SELinux and somewhat reduce its use in btrfs.
>
> Hold on... actually I just realized that with FS_HANDLES_LSM_OPTS it
> is possible to do btrfs without FS_BINARY_MOUNTDATA and also eliminate
> the need for the workaround in vfs_parse_fs_param() (i.e. [2]).
>
> Basically instead of setting FS_BINARY_MOUNTDATA | FS_HANDLES_LSM_OPTS
> in btrfs_fs_type and neither in btrfs_root_fs_type, it is enough to
> set neither in btrfs_fs_type and only FS_HANDLES_LSM_OPTS in
> btrfs_root_fs_type. The security opts are then applied in the outer
> vfs_get_tree() call instead of the inner one, but the net effect is
> the same.
>
> That should pretty much do away with both the non-legit users of
> FS_BINARY_MOUNTDATA (selinux_set_mnt_opts() and btrfs). All the rest
> seem to be in line with the semantic.
>
> Would [something like] the above stand any chance of getting your approval?

So I posted this variant as v2 now:
https://lore.kernel.org/selinux/20210517134201.29271-1-omosnace@redhat.com/T/

>
> [2] https://lore.kernel.org/selinux/20210401065403.GA1363493@infradead.org/T/

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