Re: [PATCH] selinux: allow labeling before policy is loaded

[Jonathan Lebon <jlebon@redhat.com>]

On Tue, Aug 27, 2019 at 8:56 PM Paul Moore <paul@paul-moore.com> wrote:
> As I'm looking at this, I'm wondering why we don't just bail out early
> if the policy isn't loaded?  The context lookup and permission checks
> later in the function are pretty much useless if the policy hasn't
> been loaded (they are just going to return defaults/allow), I think
> the only thing we would need to check would be
> inode_owner_or_capable().

Yes, I think you're correct. Though in that case, would it make sense
to just do the inode_owner_or_capable() check once upfront instead?

  int selinux_inode_setxattr(...)
  {

    if (strcmp(name, XATTR_NAME_SELINUX)) {
      ...
    }

    if (!inode_owner_or_capable(inode)
      ...

    if (!selinux_state.initialized)
      return 0;

    if (sbsec & SBLABEL_MNT)
      ...

    ...
  }

Hmm, though I guess it does change the behaviour slightly even in the
initialized case by returning EPERM first where before we might've
returned EOPNOTSUPP (I've seen userspace code which subtly relied on
the order in which the kernel checks for error conditions). I'm happy
to be conservative and go with your approach if you prefer.