Re: [PATCH] audit: optionally print warning after waiting to enqueue record

[Paul Moore <paul@paul-moore.com>]

On Tue, Jun 16, 2020 at 12:58 AM Max Englander <max.englander@gmail.com> wrote:
>
> In environments where security is prioritized, users may set
> --backlog_wait_time to a high value in order to reduce the likelihood
> that any audit event is lost, even though doing so may result in
> unpredictable performance if the kernel schedules a timeout when the
> backlog limit is exceeded. For these users, the next best thing to
> predictable performance is the ability to quickly detect and react to
> degraded performance. This patch proposes to aid the detection of kernel
> audit subsystem pauses through the following changes:
>
> Add a variable named audit_backlog_warn_time. Enforce the value of this
> variable to be no less than zero, and no more than the value of
> audit_backlog_wait_time.
>
> If audit_backlog_warn_time is greater than zero and if the total time
> spent waiting to enqueue an audit record is greater than or equal to
> audit_backlog_warn_time, then print a warning with the total time
> spent waiting.
>
> An example configuration:
>
>         auditctl --backlog_warn_time 50
>
> An example warning message:
>
>         audit: sleep_time=52 >= audit_backlog_warn_time=50
>
> Tested on Ubuntu 18.04.04 using complementary changes to the audit
> userspace: https://github.com/linux-audit/audit-userspace/pull/131.
>
> Signed-off-by: Max Englander <max.englander@gmail.com>
> ---
>  include/uapi/linux/audit.h |  7 ++++++-
>  kernel/audit.c             | 35 +++++++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+), 1 deletion(-)

If an admin is prioritizing security, aka don't loose any audit
records, and there is a concern over variable system latency due to an
audit queue backlog, why not simply disable the backlog limit?

-- 
paul moore
www.paul-moore.com

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