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From:   Andy Lutomirski <luto@kernel.org>
Date:   Fri, 24 May 2019 12:30:44 -0700
Message-ID: <CALCETrVp+r_wz=sOwLC8oW2P54r=sudBtV+J-Ycq_JE2QxwxEQ@mail.gmail.com>
Subject: Re: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     "Xing, Cedric" <cedric.xing@intel.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Andy Lutomirski <luto@kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        LSM List <linux-security-module@vger.kernel.org>,
        Paul Moore <paul@paul-moore.com>,
        Eric Paris <eparis@parisplace.org>,
        "selinux@vger.kernel.org" <selinux@vger.kernel.org>,
        Jethro Beekman <jethro@fortanix.com>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Dr. Greg" <greg@enjellic.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
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        David Rientjes <rientjes@google.com>
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On Fri, May 24, 2019 at 12:13 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Fri, May 24, 2019 at 11:34:32AM -0700, Xing, Cedric wrote:
> > > From: linux-sgx-owner@vger.kernel.org [mailto:linux-sgx-
> > > owner@vger.kernel.org] On Behalf Of Sean Christopherson
> > > Sent: Friday, May 24, 2019 10:55 AM

> I don't see a fundamental difference between having RWX in an enclave and
> RWX in normal memory, either way the process can execute arbitrary code,
> i.e. PROCESS__EXECMEM is appropriate.  Yes, an enclave will #UD on certain
> instructions, but that's easily sidestepped by having a trampoline in the
> host (marked RX) and piping arbitrary code into the enclave.  Or using
> EEXIT to do a bit of ROP.

There's a difference, albeit a somewhat weak one, if sigstructs are
whitelisted.  FILE__EXECMOD on
either /dev/sgx/enclave or on the sigstruct is not an entirely crazy
way to express this.