Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device.

[Luis Chamberlain <mcgrof@kernel.org>]

On Fri, Mar 11, 2022 at 01:53:03PM -0500, Paul Moore wrote:
> On Fri, Mar 11, 2022 at 12:56 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
> >
> > On Tue, Mar 08, 2022 at 08:50:53PM +0530, Kanchan Joshi wrote:
> > > diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> > > index 5c9cd9695519..1df270b47af5 100644
> > > --- a/drivers/nvme/host/ioctl.c
> > > +++ b/drivers/nvme/host/ioctl.c
> > > @@ -369,6 +469,33 @@ long nvme_ns_chr_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> > >       return __nvme_ioctl(ns, cmd, (void __user *)arg);
> > >  }
> > >
> > > +static int nvme_ns_async_ioctl(struct nvme_ns *ns, struct io_uring_cmd *ioucmd)
> > > +{
> > > +     int ret;
> > > +
> > > +     BUILD_BUG_ON(sizeof(struct nvme_uring_cmd_pdu) > sizeof(ioucmd->pdu));
> > > +
> > > +     switch (ioucmd->cmd_op) {
> > > +     case NVME_IOCTL_IO64_CMD:
> > > +             ret = nvme_user_cmd64(ns->ctrl, ns, NULL, ioucmd);
> > > +             break;
> > > +     default:
> > > +             ret = -ENOTTY;
> > > +     }
> > > +
> > > +     if (ret >= 0)
> > > +             ret = -EIOCBQUEUED;
> > > +     return ret;
> > > +}
> >
> > And here I think we'll need something like this:
> 
> If we can promise that we will have a LSM hook for all of the
> file_operations::async_cmd implementations that are security relevant
> we could skip the LSM passthrough hook at the io_uring layer.

There is no way to ensure this unless perhaps we cake that into
the API somehow... Or have a registration system for setting the
respctive file ops / LSM.

> It
> would potentially make life easier in that we don't have to worry
> about putting the passthrough op in the right context, but risks
> missing a LSM hook control point (it will happen at some point and
> *boom* CVE).

Precicely my concern. So we either open code this and ask folks
to do this or I think we do a registration and require both ops
and the the LSM hook at registration.

I think this should be enough information to get Kanchan rolling
on the LSM side.

  Luis