Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()

Jarkko Sakkinen
2020-09-24T21:58:30Z

On Thu, Sep 24, 2020 at 12:28:54PM -0700, Sean Christopherson wrote:
> 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.

I think it makes sense as long as it is not half-way there solution.

Either require it for the full binary or not at all. I'm fine with
either.

/Jarkko