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    SubjectRe: [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@linux.ibm.com>
    >>
    >> 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@linux.ibm.com>
    >> ---
    > 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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