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Subject: Re: [PATCH] kconfig: Add kernel config option for fuzz testing.
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To:     Matthew Garrett <mjg59@google.com>,
        Dmitry Vyukov <dvyukov@google.com>
Cc:     Andi Kleen <ak@linux.intel.com>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, Jiri Slaby <jslaby@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>
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Date:   Fri, 28 Feb 2020 07:10:12 +0900
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On 2020/02/18 19:54, Tetsuo Handa wrote:
> On 2020/01/03 4:57, Matthew Garrett wrote:
>> On Tue, Dec 17, 2019 at 12:53 AM Dmitry Vyukov <dvyukov@google.com> wrote:
>>> +Matthew for a lockdown question
>>> We are considering [ab]using lockdown (you knew this will happen!) for
>>> fuzzing kernel. LOCKDOWN_DEBUGFS is a no-go for us and we may want a
>>> few other things that may be fuzzing-specific.
>>> The current inflexibility comes from the global ordering of levels:
>>>
>>> if (kernel_locked_down >= level)
>>> if (kernel_locked_down >= what) {
>>>
>>> Is it done for performance? Or for simplicity?
>>
>> Simplicity. Based on discussion, we didn't want the lockdown LSM to
>> enable arbitrary combinations of lockdown primitives, both because
>> that would make it extremely difficult for userland developers and
>> because it would make it extremely easy for local admins to
>> accidentally configure policies that didn't achieve the desired
>> outcome. There's no inherent problem in adding new options, but really
>> right now they should fall into cases where they're protecting either
>> the integrity of the kernel or preventing leakage of confidential
>> information from the kernel.
>>
> 
> Can we resume this topic?
> 
> I think build-time lockdown (i.e. kernel config option) is more reliable
> and easier to use.
> 

Here is an example of need to lockdown specific ations. Can we proceed?

https://lkml.kernel.org/r/CACT4Y+azQXLcPqtJG9zbj8hxqw4jE3dcwUj5T06bdL3uMaZk+Q@mail.gmail.com