Re: [PATCH v9 11/23] ima: Move ima_lsm_policy_notifier into ima_namespace

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On 1/26/22 08:05, Christian Brauner wrote:
On Tue, Jan 25, 2022 at 05:46:33PM -0500, Stefan Berger wrote:
From: Stefan Berger <stefanb@xxxxxxxxxxxxx>

Move the ima_lsm_policy_notifier into the ima_namespace. Each IMA
namespace can now register its own LSM policy change notifier callback.
The policy change notifier for the init_ima_ns still remains in init_ima()
and therefore handle the registration of the callback for all other
namespaces in init_ima_namespace().

Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
---
I'd double-check that this cannot be used to cause rcu stalls when a lot
of ima namespace with a lot of rules are used leading to a dos situation
during LSM policy update. The good thing at least is that an LSM policy
update can only be triggered for selinux for the whole system.


I just ran a test with up to 1920 IMA-namespaces each with 2 audit rules with the vmtools_exec_t label. Disabling of the vmtools SELinux module caused the rules to disappear in all IMA namespaces, as expected. However, it also added many kernel log lines 'ima: rule for LSM 'vmtools_exec_t' is undefined' to the kernel log that should probably be suppressed for ns != &init_ima_ns. Nothing bad happened otherwise. Also re-enabling the vmtools module didn't cause any kernel errors.  So I think we should be fine.

https://github.com/stefanberger/ima-namespaces-tests/tree/master/audit-many-2





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