Re: [RFC 1/1] Use ioctl selinux callback io_uring commands that implement the ioctl op convention

Luis Chamberlain
2022-11-21T19:54:23Z

On Thu, Nov 17, 2022 at 05:10:07PM -0500, Paul Moore wrote:
> On Thu, Nov 17, 2022 at 4:40 AM Joel Granados <j.granados@samsung.com> wrote:
> > On Wed, Nov 16, 2022 at 02:21:14PM -0500, Paul Moore wrote:
>
> ...
>
> > > * As we discussed previously, the real problem is the fact that we are
> > > missing the necessary context in the LSM hook to separate the
> > > different types of command targets. With traditional ioctls we can
> > > look at the ioctl number and determine both the type of
> > > device/subsystem/etc. as well as the operation being requested; there
> > > is no such information available with the io_uring command
> > > passthrough. In this sense, the io_uring command passthrough is
> > > actually worse than traditional ioctls from an access control
> > > perspective. Until we have an easy(ish)[1] way to determine the
> > > io_uring command target type, changes like the one suggested here are
> > > going to be doomed as each target type is free to define their own
> > > io_uring commands.
> >
> > The only thing that comes immediately to mind is that we can have
> > io_uring users define a function that is then passed to the LSM
> > infrastructure. This function will have all the logic to give relative
> > context to LSM. It would be general enough to fit all the possible commands
> > and the logic would be implemented in the "drivers" side so there is no
> > need for LSM folks to know all io_uring users.
>
> Passing a function pointer to the LSM to fetch, what will likely be
> just a constant value, seems kinda ugly, but I guess we only have ugly
> options at this point.

I am not sure if this helps yet, but queued on modules-next we now have
an improvement in speed of about 1500x for kallsyms_lookup_name(), and
so symbol lookups are now fast. Makes me wonder if a type of special
export could be drawn up for specific calls which follow a structure
and so the respective lsm could be inferred by a prefix instead of
placing the calls in-place. Then it would not mattter where a call is
used, so long as it would follow a specific pattern / structure with
all the crap you need on it.

Luis