linux-kernel - Re: Re: [PATCH v12 00/18] Enable FSGSBASE instructions

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Message-ID: <F8D68F56-8928-489A-92AD-175048B22A6F@zytor.com>
Date:   Sun, 24 May 2020 16:44:40 -0700
From:   hpa@...or.com
To:     Sasha Levin <sashal@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Don Porter <porter@...unc.edu>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        bp@...en8.de, luto@...nel.org, dave.hansen@...el.com,
        tony.luck@...el.com, ravi.v.shankar@...el.com,
        chang.seok.bae@...el.com
Subject: Re: Re: [PATCH v12 00/18] Enable FSGSBASE instructions

On May 24, 2020 2:19:45 PM PDT, Sasha Levin <sashal@...nel.org> wrote:
>On Sun, May 24, 2020 at 12:45:18PM -0700, hpa@...or.com wrote:
>>There are legitimate reasons to write a root-hole module, the main one
>being able to test security features like SMAP. I have requested before
>a TAINT flag specifically for this purpose, because TAINT_CRAP is
>nowhere near explicit enough, and is also used for staging drivers.
>Call it TAINT_TOXIC or TAINT_ROOTHOLE; it should always be accompanied
>with a CRIT level alert.
>
>What I don't like about our current system of TAINT_* flags is that
>while we can improve it as much as we want, no one outside of the
>kernel
>tree seems to be using it. While Thomas may have been commenting on
>Graphene's behaviour, look at any other code that did the same thing:
>
>- Graphene:
>https://github.com/oscarlab/graphene-sgx-driver/blob/master/gsgx.c
>- Occlum:
>https://github.com/occlum/enable_rdfsbase/blob/master/enable_rdfsbase.c
>- SGX-LKL:
>https://github.com/lsds/sgx-lkl/blob/master/tools/kmod-set-fsgsbase/mod_set_cr4_fsgsbase.c
>
>None of which set even the CRAP flag.

That's a separate problem, but I would personally want to have it for my own test modules in case one ever escapes.
-- 
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