linux-kernel - Re: [PATCH v20 00/28] Intel SGX1 support

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Date:   Mon, 22 Apr 2019 10:17:15 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Dr. Greg" <greg@...ellic.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jethro Beekman <jethro@...tanix.com>,
        Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Borislav Petkov <bp@...en8.de>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v20 00/28] Intel SGX1 support

On Mon, Apr 22, 2019 at 09:55:47AM -0700, Linus Torvalds wrote:
> On Mon, Apr 22, 2019 at 9:48 AM Sean Christopherson
> <sean.j.christopherson@...el.com> wrote:
> >
> > Right, and loading a malicious enclave doesn't change those guarantees
> > (for other enclaves).  Ergo, restricting which enclaves can execute is
> > orthogonal to the security provided by SGX.
> 
> But it is absolutely worth noting that TSX made a lot of attacks both
> easier to _do_, and also easier to _hide_.
> 
> All while being basically completely worthless technology to everybody
> except for some silly SAP benchmark.
> 
> So it is definitely worth at least discussing the downsides of SGX. If
> it ends up being another technology that makes it easier to create
> malware, without actually having a lot of _good_ software use it, the
> patches to enable it should make damn sure that the upsides actually
> outweigh the downsides.
> 
> And if the current setup basically is "you have to disable reasonable
> SElinux protections that lots of distros use today", I think it's
> entirely reasonable saying "the downsides are bigger than the
> upsides".

I'm not arguing against SGX playing nice with SELinux/LSMs, actually the
opposite.  I completely agree that enclaves should be subject to LSM
restrictions.

AIUI, Dr. Greg is proposing a framework that uses SGX's launch control
mechanism to restrict what enclaves can run.  My point is that restricting
what enclaves can run is about protecting the kernel and/or platform, not
the enclaves themselves, i.e. using launch control instead of, or in
addition to, LSMs doesn't change the security guarantees of SGX.