linux-kernel - Re: [RFC,v1,1/1] audit: speed up syscall rule match while exiting syscall

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Date:   Wed, 13 Jan 2021 08:47:56 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     yang.yang29@....com.cn
Cc:     Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC,v1,1/1] audit: speed up syscall rule match while exiting syscall

On Wed, Jan 13, 2021 at 7:39 AM <yang.yang29@....com.cn> wrote:
> From 82ebcf43481be21ee3e32ec1749b42f651737880 Mon Sep 17 00:00:00 2001
> From: Yang Yang <yang.yang29@....com.cn>
> Date: Wed, 13 Jan 2021 20:18:04 +0800
> Subject: [PATCH] [RFC,v1,1/1] speed up syscall rule match while exiting syscall
>  If user add any syscall rule, in all syscalls, audit_filter_syscall()
>  traverses struct list_head audit_filter_list to find out whether current
>  syscall match one rule. This takes o(n), which is not necessary, specially
>  for user who add a very few syscall rules. On the other hand, user may not
>  much care about rule add/delete speed. So do o(n) calculate at rule changing,
>  and ease the burden of audit_filter_syscall().
>
>  Define audit_syscall[NR_syscalls], every element stands for one syscall.
>  audit_filter_syscall() checks audit_syscall[NR_syscalls].
>  audit_syscall[n] == 0 indicates no rule audit syscall n, do a quick exit.
>  audit_syscall[n] > 0 indicates at least one rule audit syscall n.
>  audit_syscall[n] update when syscall rule changes.
>
> Signed-off-by: Yang Yang <yang.yang29@....com.cn>
> ---
>  include/linux/audit.h |  2 ++
>  kernel/audit.c        |  2 ++
>  kernel/auditfilter.c  | 16 ++++++++++++++++
>  kernel/auditsc.c      |  9 ++++++++-
>  4 files changed, 28 insertions(+), 1 deletion(-)

Before we go too far into a review of this patch, please provide some
performance measurements using a variety of rule counts, both common
and extreme, so that we can better judge the benefits of this patch.
The measurements should include both the rule add/delete time deltas
as well as the impact on the syscall invocations.  If non-obvious,
please also include how you performed the measurements and captured
the data.

These are good things to include in the commit description when
submitting patches focused on improving performance.

-- 
paul moore
www.paul-moore.com