From: Kees Cook <keescook@chromium.org>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>,
linux-security-module@vger.kernel.org, bpf@vger.kernel.org,
paul@paul-moore.com, casey@schaufler-ca.com, song@kernel.org,
daniel@iogearbox.net, ast@kernel.org, renauld@google.com
Subject: Re: [PATCH v4 0/5] Reduce overhead of LSMs with static calls
Date: Mon, 25 Sep 2023 15:02:10 -0700 [thread overview]
Message-ID: <202309251500.B80E2D66@keescook> (raw)
In-Reply-To: <CAGudoHHm-ofzATMdE_HU2e0voKiQnkkcL+1+F73azxNeHCvYSA@mail.gmail.com>
On Mon, Sep 25, 2023 at 10:08:39PM +0200, Mateusz Guzik wrote:
> On 9/24/23, Kees Cook <keescook@chromium.org> wrote:
> > That said, I've long advocated[1] for a way to explicitly disable LSMs
> > without affecting operational ordering. I think it would be very nice to
> > be able to boot with something like:
> >
> > lsm=!yama
> >
> > to disable Yama. Or for your case, "lsm=!tomoyo". Right now, you have to
> > figure out what the lsm list is, and then create a new one with the
> > LSM you want disabled removed from the list. i.e. with v6.2 and later
> > check the boot log, and you'll see:
> >
> > LSM: initializing lsm=lockdown,capability,landlock,yama,integrity,apparmor
> >
> > If you wanted to boot with Yama removed, you'd then pass:
> >
> > lsm=lockdown,capability,landlock,integrity,apparmor
> >
> > As a boot param. But I think this is fragile since now any new LSMs will
> > be by-default disabled once a sysadmin overrides the "lsm" list. Note
> > that booting with "lsm.debug=1" will show even more details. See commit
> > 86ef3c735ec8 ("LSM: Better reporting of actual LSMs at boot").
> >
> > So, if a distro has no support for an LSM but they want it _available_
> > in the kernel, they should leave it built in, but remove it from the
> > "lsm=" list. That's a reasonable bug to file against a distro...
> >
>
> Maybe I once more expressed myself poorly, I meant to say stock Debian
> does not ship any tooling for tomoyo, but the kernel has support
> compiled in.
If there is no tooling Debian should either not build the support into
the kernel or should leave it out of the CONFIG_LSM list.
> Ultimately, after stacking got implemented, it was inevitable diestros
> like Debian will enable whatever modules and expect them to not be a
> problem if not configured by userspace.
>
> I don't think any form of messing with CONFIG_LSM is a viable option,
> even if you make it a boot param.
>
> What should happen instead is that modules which are not given any
> config don't get in the way.
Right -- this is an open problem, and I think we can solve it using the
static_call system (much like how the BPF LSM is doing it).
-Kees
--
Kees Cook
prev parent reply other threads:[~2023-09-25 22:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-22 14:55 [PATCH v4 0/5] Reduce overhead of LSMs with static calls KP Singh
2023-09-22 14:55 ` [PATCH v4 1/5] kernel: Add helper macros for loop unrolling KP Singh
2023-09-22 14:55 ` [PATCH v4 2/5] security: Count the LSMs enabled at compile time KP Singh
2023-09-22 15:50 ` Kees Cook
2023-09-22 16:07 ` KP Singh
2023-09-27 22:37 ` KP Singh
2023-09-22 14:55 ` [PATCH v4 3/5] security: Replace indirect LSM hook calls with static calls KP Singh
2023-09-23 14:52 ` kernel test robot
2023-09-27 5:26 ` kernel test robot
2023-09-22 14:55 ` [PATCH v4 4/5] bpf: Only enable BPF LSM hooks when an LSM program is attached KP Singh
2023-09-22 14:55 ` [PATCH v4 5/5] security: Add CONFIG_SECURITY_HOOK_LIKELY KP Singh
2023-09-22 15:50 ` Kees Cook
2023-09-22 15:51 ` [PATCH v4 0/5] Reduce overhead of LSMs with static calls Kees Cook
2023-09-22 18:42 ` Mateusz Guzik
2023-09-23 16:16 ` KP Singh
2023-09-23 17:13 ` Mateusz Guzik
2023-09-23 17:15 ` Mateusz Guzik
2023-09-24 2:46 ` Kees Cook
2023-09-25 20:08 ` Mateusz Guzik
2023-09-25 22:02 ` Kees Cook [this message]
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