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

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Date:   Mon, 27 May 2019 16:34:31 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        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,
        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 23, 2019 at 07:17:52AM -0700, Sean Christopherson wrote:
>   1. Do nothing.  Userspace would essentially be required to mmap() the
>      enclave after EINIT, which is ugly but not breaking since userspace
>      could mmap() the enclave with a placeholder VMA prior to building
>      the enclave, and then a series of mmap() to establish its "real"
>      mapping.

What it'd break to return error if mmap() is done before EINIT?

>   2. Propagate the permissions from EADD to the VMAs of the current mm
>      if the entire EADD range is mapped and the mapping is PROT_NONE.

Right now you can do multiple mmap's. If the mmap's must be done after
EINIT, the driver could check that permissions match the permissions in
that range.

This leaves open how to deal with mprotect() but if the process does not
have FILE__WRITE I guess you cannot do much.

>   3. Propagate the permissions from EADD to the VMAs of all mm structs
>      that have mapped some piece of the enclave, following the matching
>      rules from #2.

For me it looks that allowing mmap's only after EINIT would result the
least confusing implemntation.

/Jarkko