From: Paul Moore <[email protected]>
To: Luis Chamberlain <[email protected]>
Cc: Joel Granados <[email protected]>,
Kanchan Joshi <[email protected]>,
[email protected], [email protected],
[email protected]
Subject: Re: [RFC 1/1] Use ioctl selinux callback io_uring commands that implement the ioctl op convention
Date: Mon, 21 Nov 2022 16:05:37 -0500 [thread overview]
Message-ID: <CAHC9VhR+RFqJ7c6mFhnMFdDXPcCBg-pnAzEuyOc-TX5hmsubwg@mail.gmail.com> (raw)
In-Reply-To: <Y3vXLQz1k8E/[email protected]>
On Mon, Nov 21, 2022 at 2:53 PM Luis Chamberlain <[email protected]> wrote:
> On Thu, Nov 17, 2022 at 05:10:07PM -0500, Paul Moore wrote:
> > On Thu, Nov 17, 2022 at 4:40 AM Joel Granados <[email protected]> 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.
I suspect we may be talking about different things here, I don't think
the issue is which LSM(s) may be enabled, as the call is to
security_uring_cmd() regardless. I believe the issue is more of how
do the LSMs determine the target of the io_uring command, e.g. nvme or
ublk.
My understanding is that Joel was suggesting a change to the LSM hook
to add a function specific pointer (presumably defined as part of the
file_operations struct) that could be called by the LSM to determine
the target.
Although now that I'm looking again at the file_operations struct, I
wonder if we would be better off having the LSMs inspect the
file_operations::owner field, potentially checking the module::name
field. It's a little painful in the sense that it is potentially
multiple strcmp() calls for each security_uring_cmd() call, but I'm
not sure the passed function approach would be much better. Do we
have a consistent per-module scalar value we can use instead of a
character string?
--
paul-moore.com
next prev parent reply other threads:[~2022-11-21 21:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20221116125430eucas1p2f2969a4a795614ce3b8c06f9ea3be36f@eucas1p2.samsung.com>
2022-11-16 12:50 ` [RFC 0/1] RFC on how to include LSM hooks for io_uring commands Joel Granados
[not found] ` <CGME20221116125431eucas1p1dfd03b80863fce674a7c662660c94092@eucas1p1.samsung.com>
2022-11-16 12:50 ` [RFC 1/1] Use ioctl selinux callback io_uring commands that implement the ioctl op convention Joel Granados
2022-11-16 17:38 ` Kanchan Joshi
2022-11-16 19:21 ` Paul Moore
2022-11-17 9:40 ` Joel Granados
2022-11-17 22:10 ` Paul Moore
2022-11-21 19:53 ` Luis Chamberlain
2022-11-21 21:05 ` Paul Moore [this message]
2022-11-22 11:18 ` Joel Granados
2022-11-22 14:04 ` Ming Lei
2022-11-28 10:13 ` Joel Granados
2022-11-28 10:59 ` Ming Lei
2022-11-22 11:15 ` Joel Granados
2022-11-17 9:25 ` Joel Granados
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