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Subject: Re: [PATCH v5 01/13] taint: Introduce a new taint flag (insecure)
To:     Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>
Cc:     "Chang S. Bae" <chang.seok.bae@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
        Markus T Metzger <markus.t.metzger@intel.com>,
        Ravi Shankar <ravi.v.shankar@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
References: <20190201205319.15995-1-chang.seok.bae@intel.com>
 <20190201205319.15995-2-chang.seok.bae@intel.com>
 <CALCETrXi=PEOXCQYkCO9BLL+oaoJonRohWoxvUqxZdiWURc3=Q@mail.gmail.com>
 <20190205132146.2e61b3df9e7be49e22b7d903@linux-foundation.org>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <f41a5d14-b642-0969-3c7a-cc12b820d208@infradead.org>
Date:   Tue, 5 Feb 2019 14:46:11 -0800
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On 2/5/19 1:21 PM, Andrew Morton wrote:
> On Fri, 1 Feb 2019 18:42:29 -0800 Andy Lutomirski <luto@kernel.org> wrote:
> 
>> On Fri, Feb 1, 2019 at 12:54 PM Chang S. Bae <chang.seok.bae@intel.com> wrote:
>>>
>>> For testing (or root-only) purposes, the new flag will serve to tag the
>>> kernel taint accurately.
>>>
>>> When adding a new feature support, patches need to be incrementally
>>> applied and tested with temporal parameters. Currently, there is no flag
>>> for this usage.
>>
>> I think this should be reviewed by someone like akpm.  akpm, for
>> background, this is part of an x86 patch series.  If only part of the
>> series is applied, the kernel will be blatantly insecure (but still
>> functional and useful for testing and bisection), and this taint flag
>> will be set if this kernel is booted.  With the whole series applied,
>> there are no users of the taint flag in the kernel.
>>
>> Do you think this is a good idea?
> 
> What does "temporal parameters" mean?  A complete description of this
> testing process would help.
> 
> I sounds a bit strange.  You mean it assumes that people will partially
> apply the series to test its functionality?  That would be inconvenient.

Ack.  I don't think we need to (or should) worry about that kind of
muckup.

> - Can the new and now-unused taint flag be removed again at
>   end-of-series?
> 
> - It would be a lot more convenient if we had some means of testing
>   after the whole series is applied, on a permanent basis - some
>   debugfs flag, perhaps?
> 


-- 
~Randy