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Subject: Re: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <20190524170704.GA3401@linux.intel.com>
Date:   Fri, 24 May 2019 10:51:02 -0700
Cc:     Andy Lutomirski <luto@kernel.org>,
        "Xing, Cedric" <cedric.xing@intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        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>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        "Svahn, Kai" <kai.svahn@intel.com>, Borislav Petkov <bp@alien8.de>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        David Rientjes <rientjes@google.com>
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References: <20190522153836.GA24833@linux.intel.com> <CALCETrUS8xyF1JJmQs18BGTDhPRXf+s81BkMZCZwmY73r7M+zg@mail.gmail.com> <20190523023517.GA31950@linux.intel.com> <20190523102628.GC10955@linux.intel.com> <20190523141752.GA12078@linux.intel.com> <CALCETrUzx3LPAKCLFf75P-XshAkRcr+JLET3LA_kHDs9MA11FA@mail.gmail.com> <20190523234044.GC12078@linux.intel.com> <CALCETrV4DVEfW6EJ6DnQGGYDJAiA5M1QcuYJTiroumOM+D6Jjg@mail.gmail.com> <960B34DE67B9E140824F1DCDEC400C0F654E8956@ORSMSX116.amr.corp.intel.com> <CALCETrX0WqouSWgdM+LNxMzypa0ZHZXTmJ+nNkuPuL8UOF_f2w@mail.gmail.com> <20190524170704.GA3401@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On May 24, 2019, at 10:07 AM, Sean Christopherson <sean.j.christopherson@i=
ntel.com> wrote:
>=20
>> 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@intel.com> wr=
ote:
>>> /**
>>> * Summary:
>>> * - The enclave file resembles a shared object that contains RO/RX/RW se=
gments
>>> * - FILE__* are assigned to /dev/sgx/enclave, to determine acceptable pe=
rmissions to mmap()/mprotect(), valid combinations are
>>> *   + FILE__READ - Allow SGX1 enclaves only
>>> *   + FILE__READ|FILE__WRITE - Allow SGX2 enclaves to expand data segmen=
ts (e.g. heaps, stacks, etc.)
>>=20
>> 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.
>=20
> 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 =E2=80=94 FILE__WRITE on the enclave file on disk is no g=
ood.=