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Date:   Fri, 25 Sep 2020 00:55:23 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Haitao Huang <haitao.huang@linux.intel.com>
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
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        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        asapek@google.com, Borislav Petkov <bp@alien8.de>,
        "Xing, Cedric" <cedric.xing@intel.com>, chenalexchen@google.com,
        Conrad Parker <conradparker@google.com>, cyhanish@google.com,
        Dave Hansen <dave.hansen@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
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        Neil Horman <nhorman@redhat.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Patrick Uiterwijk <puiterwijk@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Thomas Gleixner <tglx@linutronix.de>, yaozhangx@google.com
Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()
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On Thu, Sep 24, 2020 at 02:11:37PM -0500, Haitao Huang wrote:
> > For me this has caused months of confusion and misunderstanding of this
> > feature. I only recently realized that "oh, right, we invented this".
> > 
> > They are contrived scenarios enough that they should be considered when
> > the workloads hit.
> > 
> > Either we fully support noexec or not at all. Any "partial" thing is a
> > two edged sword: it can bring some robustness with the price of
> > complexity and possible unknown uknown scenarios where they might become
> > API issue.
> > 
> > I rather think later on how to extend API in some way to enable such
> > contrivid scenarios rather than worrying about how this could be abused.
> > 
> > The whole SGX is complex beast already so lets not add any extra when
> > there is no a hard requirement to do so.
> > 
> > I'll categorically deny noexec in the next patch set version.
> > 
> > /Jarkko
> 
> There are use cases supported currently in which enclave binary is received
> via IPC/RPC and held in buffers before EADD. Denying noexec altogether would
> break those, right?

I do not see why data cannot be provided at run-time. AFAIK, it is not
different from executables how this works when it comes to noexec.

/Jarkko