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

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Date:   Mon, 20 May 2019 14:41:05 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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,
        Jethro Beekman <jethro@...tanix.com>,
        "Xing, Cedric" <cedric.xing@...el.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 Thu, May 16, 2019 at 05:26:15PM -0700, Andy Lutomirski wrote:
> Is userspace actually requred to mmap() the enclave prior to EADDing things?

Nope, not since v20. Here is what I wrote about API to the kernel
documentation:

"The enclave life-cycle starts by opening `/dev/sgx/enclave`. After this
there is already a data structure inside kernel tracking the enclave
that is initially uncreated. After this a set of ioctl's can be used to
create, populate and initialize the enclave.

You can close (if you want) the fd after you've mmap()'d. As long as the
file is open the enclave stays alive so you might want to do that after
you don't need it anymore. Even munmap() won't destruct the enclave if
the file is open.  Neither will closing the fd as long as you have
mmap() done over the fd (even if it does not across the range defined in
SECS)."

Enclave can be created and initialized without doing a single mmap()
call.

/Jarkko