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

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Message-ID: <alpine.DEB.2.21.1904192329490.3174@nanos.tec.linutronix.de>
Date:   Fri, 19 Apr 2019 23:34:46 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jethro Beekman <jethro@...tanix.com>
cc:     Andy Lutomirski <luto@...capital.net>,
        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 Fri, 19 Apr 2019, Jethro Beekman wrote:
> On 2019-04-19 14:15, Andy Lutomirski wrote:
> > With plain mmap() + mprotect(), the LSM will prevent you from making
> > memory that *was* writable executable.  This is by design and SELinux
> > supports it.  I don’t remember the name of the associated SELinux
> > permission off the top of my head.
> >
> > 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.

And how so? You create writeable AND executable memory. That's a nono and
you can argue in circles, that's not going to change with any of your
proposed changes. Andy clearly made a proposal which solves it in a proper
way.

Thanks,

	tglx