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Date:   Mon, 17 Jun 2019 19:38:47 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Cedric Xing <cedric.xing@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,
        Jethro Beekman <jethro@fortanix.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        linux-sgx@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>, nhorman@redhat.com,
        npmccallum@redhat.com, Serge Ayoun <serge.ayoun@intel.com>,
        Shay Katz-zamir <shay.katz-zamir@intel.com>,
        Haitao Huang <haitao.huang@intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Kai Svahn <kai.svahn@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Josh Triplett <josh@joshtriplett.org>,
        Kai Huang <kai.huang@intel.com>,
        David Rientjes <rientjes@google.com>,
        William Roberts <william.c.roberts@intel.com>,
        Philip Tricca <philip.b.tricca@intel.com>
Subject: Re: [RFC PATCH v2 5/5] security/selinux: Add enclave_load()
 implementation
Message-ID: <20190617163655.GA8710@linux.intel.com>
References: <20190606021145.12604-1-sean.j.christopherson@intel.com>
 <20190606021145.12604-6-sean.j.christopherson@intel.com>
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On Wed, Jun 05, 2019 at 07:11:45PM -0700, Sean Christopherson wrote:
> The goal of selinux_enclave_load() is to provide a facsimile of the
> existing selinux_file_mprotect() and file_map_prot_check() policies,
> but tailored to the unique properties of SGX.
> 
> For example, an enclave page is technically backed by a MAP_SHARED file,
> but the "file" is essentially shared memory that is never persisted
> anywhere and also requires execute permissions (for some pages).
> 
> The basic concept is to require appropriate execute permissions on the
> source of the enclave for pages that are requesting PROT_EXEC, e.g. if
> an enclave page is being loaded from a regular file, require
> FILE__EXECUTE and/or FILE__EXECMOND, and if it's coming from an
> anonymous/private mapping, require PROCESS__EXECMEM since the process
> is essentially executing from the mapping, albeit in a roundabout way.
> 
> Note, FILE__READ and FILE__WRITE are intentionally not required even if
> the source page is backed by a regular file.  Writes to the enclave page
> are contained to the EPC, i.e. never hit the original file, and read
> permissions have already been vetted (or the VMA doesn't have PROT_READ,
> in which case loading the page into the enclave will fail).
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>

In the end of the day, the main problem with this patch is that the
existing LSM hooks are generic. I don't we can have specific hooks
for proprietary hardware.

/Jarkko