On Fri, Jan 28, 2022 at 3:28 AM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
> On Thu, Jan 27, 2022 at 4:54 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> 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. To be affected by this, someone would need
to:
1. Use the new mount API, which:
a) doesn't even have man pages yet,
b) isn't even used by the mount(8) utility yet.
2. Call fsconfig(2) with a SELinux mount option before policy is loaded.
3. Call fsmount(2) with the same fd after policy is loaded.
And racing with the policy load doesn't count - that could fail
randomly with or without the change. I honestly can't imagine any
realistic scenario where someone would do this...
--
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.
