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Date:   Thu, 24 Sep 2020 12:28:54 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Haitao Huang <haitao.huang@linux.intel.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jethro Beekman <jethro@fortanix.com>,
        Darren Kenny <darren.kenny@oracle.com>,
        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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        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()
Message-ID: <20200924192853.GA18826@linux.intel.com>
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On Thu, Sep 24, 2020 at 02:11:37PM -0500, Haitao Huang wrote:
> On Wed, 23 Sep 2020 08:50:56 -0500, Jarkko Sakkinen
> <jarkko.sakkinen@linux.intel.com> wrote:
> >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?

No.  noexec only applies to file-backed VMAs, what you're describing is loading
an enclave from an anon VMA, which will still have VM_MAYEXEC.

I believe you're thinking of SELinux's EXECMEM, which is required to execute
from anonymous memory, and which we talked about (more than once) applying to
SGX enclaves.

That being said, I still dislike the idea of requiring VM_MAYEXEC, it's a hack
that doesn't really buy us much, if anything.