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

[Ming Lei]

On Tue, Jul 19, 2022 at 10:17:17AM +0530, Kanchan Joshi wrote:
> On Mon, Jul 18, 2022 at 05:52:01PM -0400, Paul Moore wrote:
> > 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?
> 
> Earlier testing was done using fio. liburing tests need a formal review
> in list. Tree is here -
> https://github.com/ankit-sam/liburing/tree/uring-pt
> It adds new "test/io_uring_passthrough.t", which can be run this way:
> 
> ./test/io_uring_passthrough.t /dev/ng0n1
> 
> Requires nvme device (/dev/ng0n1). And admin-access as well, as this
> is raw open. FWIW, each passthrough command (at nvme driver level) is
> also guarded by admin-access.
> 
> Ankit (CCed) has the plans to post it (will keep you guys in loop) after
> bit more testing with 5.20 branch.

Another candidate is ublksrv[1] which doesn't require any device and
is pretty easy to setup. However, the kernel side driver(ublk_drv) isn't
merged to linus tree yet, but has been in for-5.20/block.

And io_uring command is sent to both /dev/ublk-control and /dev/ublkcN.

[1] https://github.com/ming1/ubdsrv.git


Thanks,
Ming