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

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Message-Id: <D1F8869E-7431-4D73-8571-8F4F187B8632@amacapital.net>
Date:   Fri, 24 May 2019 10:51:02 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        "Xing, Cedric" <cedric.xing@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        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>,
        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)


> On May 24, 2019, at 10:07 AM, Sean Christopherson <sean.j.christopherson@...el.com> wrote:
> 
>> On Fri, May 24, 2019 at 09:43:27AM -0700, Andy Lutomirski wrote:
>>> On Fri, May 24, 2019 at 12:24 AM Xing, Cedric <cedric.xing@...el.com> wrote:
>>> /**
>>> * Summary:
>>> * - The enclave file resembles a shared object that contains RO/RX/RW segments
>>> * - FILE__* are assigned to /dev/sgx/enclave, to determine acceptable permissions to mmap()/mprotect(), valid combinations are
>>> *   + FILE__READ - Allow SGX1 enclaves only
>>> *   + FILE__READ|FILE__WRITE - Allow SGX2 enclaves to expand data segments (e.g. heaps, stacks, etc.)
>> 
>> I think this is a non-starter :(  FILE__WRITE also means that you can
>> write to the file, and the admin / policy author will almost never
>> want to allow that.
> 
> Why would FILE__WRITE on /dev/sgx/enclave be a problem?  An actual
> write to /dev/sgx/enclave would yield -EINVAL, no?

Bah, read it wrong — FILE__WRITE on the enclave file on disk is no good.