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

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Message-ID: <20190527133839.GB9732@linux.intel.com>
Date:   Mon, 27 May 2019 16:38:39 +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 Mon, May 27, 2019 at 04:34:31PM +0300, Jarkko Sakkinen wrote:
> 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.

Obvious problem is of course the requirement of fixed mapping, which is
of course nasty.

/Jarkko