[PATCH v2] lsm, io_uring: add LSM hooks for the new uring_cmd file op

[Paul Moore]

On Mon, Jul 18, 2022 at 1:12 PM Casey Schaufler <casey at schaufler-ca.com> wrote:
> On 7/15/2022 8:33 PM, Paul Moore wrote:
> > On Fri, Jul 15, 2022 at 3:52 PM Paul Moore <paul at paul-moore.com> wrote:
> >> On Fri, Jul 15, 2022 at 3:28 PM Jens Axboe <axboe at kernel.dk> wrote:
> >>> On 7/15/22 1:16 PM, Luis Chamberlain wrote:
> >>>> io-uring cmd support was added through ee692a21e9bf ("fs,io_uring:
> >>>> add infrastructure for uring-cmd"), this extended the struct
> >>>> file_operations to allow a new command which each subsystem can use
> >>>> to enable command passthrough. Add an LSM specific for the command
> >>>> passthrough which enables LSMs to inspect the command details.
> >>>>
> >>>> This was discussed long ago without no clear pointer for something
> >>>> conclusive, so this enables LSMs to at least reject this new file
> >>>> operation.
> >>> From an io_uring perspective, this looks fine to me. It may be easier if
> >>> I take this through my tree due to the moving of the files, or the
> >>> security side can do it but it'd have to then wait for merge window (and
> >>> post io_uring branch merge) to do so. Just let me know. If done outside
> >>> of my tree, feel free to add:
> > I forgot to add this earlier ... let's see how the timing goes, I
> > don't expect the LSM/Smack/SELinux bits to be ready and tested before
> > the merge window opens so I'm guessing this will not be an issue in
> > practice, but thanks for the heads-up.
>
> I have a patch that may or may not be appropriate. I ran the
> liburing tests without (additional) failures, but it looks like
> there isn't anything there testing uring_cmd. Do you have a
> test tucked away somewhere I can use?

I just had a thought, would the io_uring folks be opposed if I
submitted a patch to add a file_operations:uring_cmd for the null
character device?  A simple uring_cmd noop seems to be in keeping with
the null device, and it would make testing the io_uring CMD
functionality much easier as it would not rely on a specific device.

I think something like this would be in keeping with the null driver:

  static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int
issue_flags)
  {
    return 0;
  }

Thoughts?

-- 
paul-moore.com