linux-kernel - Re: [PATCH v20 00/28] Intel SGX1 support

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Date:   Fri, 19 Apr 2019 14:31:57 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Jethro Beekman <jethro@...tanix.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "Dr. Greg" <greg@...ellic.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Borislav Petkov <bp@...en8.de>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v20 00/28] Intel SGX1 support



> On Apr 19, 2019, at 2:19 PM, Jethro Beekman <jethro@...tanix.com> wrote:
> 
>> .
>> 
>> If we start enforcing equivalent rules on SGX, then the current API will simply not allow enclaves to be loaded — no matter how you slice it, loading an enclave with the current API is indistinguishable from making arbitrary data executable.
> 
> Yes this is exactly what I intended here: a very simple change that
> stops SGX from confusing LSM. Just by enforcing that everything that
> looks like a memory write (EADD, EAUG, EDBGWR, etc.) actually requires
> write permissions, reality and LSM should be on the same page.
> 
> If you want to go further and actually allow this behavior when your LSM
> would otherwise prohibit it, presumably the same workarounds that exist
> for JITs can be used for SGX.
> 
> 

I do think we need to follow LSM rules.  But my bigger point is that there are policies that don’t allow JIT at all. I think we should arrange the SGX API so it’s still usable when such a policy is in effect.