linux-kernel - RE: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)

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Date:   Thu, 16 May 2019 23:29:47 +0000
From:   "Xing, Cedric" <cedric.xing@...el.com>
To:     "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "Andy Lutomirski" <luto@...nel.org>
CC:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Dr. Greg" <greg@...ellic.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>,
        "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: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)

> > > There is a problem here though. Usually the enclave itself is just a
> > > loader that then loads the application from outside source and
> > > creates the executable pages from the content.
> > >
> > > A great example of this is Graphene that bootstraps unmodified Linux
> > > applications to an enclave:
> > >
> > > https://github.com/oscarlab/graphene
> > >
> >
> > ISTM you should need EXECMEM or similar to run Graphene, then.
> 
> Agreed, Graphene is effectively running arbitrary enclave code.  I'm
> guessing there is nothing that prevents extending/reworking Graphene to
> allow generating the enclave ahead of time so as to avoid populating the
> guts of the enclave at runtime, i.e. it's likely possible to run an
> unmodified application in an enclave without EXECMEM if that's something
> Graphene or its users really care about.

Inefficient use of memory is a problem of running Graphene on SGX1, from at least 2 aspects: 1) heaps/stacks have to be pre-allocated but only a small portion of those pages will be actually used; and 2) dynamic linking is commonly used in *unmodified* applications and all dependent libraries have to be loaded, but only a subset of those pages will actually be used - e.g. most applications use only a small set of functions in libc.so but the whole library still has to be loaded. Hence a practical/efficient solution will require/involve EDMM features available in SGX2. I guess we shall look a bit further into future in order to address this problem properly. And I think it necessary to distinguish enclave virtual ranges from regular ones (probably at VMA level) before we could have a practical solution.