Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: pMqdgPgXTB3FFT84nUfLrVVCcf760B8H70rKT+jYSuRfXOAGavfUXCs1Huj5f65xqzNZ0Z5ya1
 dvNMsWv6bg7g==
IronPort-SDR: CUOZC+1ZeC8kxSLZJJTm5Aq8u6JZcooZlcWac/BfdJ4TSR/cRTXWeIP5QNKvuGqvyKjvppuG1D
 uvu2GvmcaJJA==
Date:   Tue, 7 Jul 2020 06:29:45 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        Jethro Beekman <jethro@fortanix.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Chunyang Hui <sanqian.hcy@antfin.com>,
        Jordan Hand <jorhand@linux.microsoft.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Seth Moore <sethmo@google.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
        asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com,
        conradparker@google.com, cyhanish@google.com,
        dave.hansen@intel.com, haitao.huang@intel.com,
        josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com,
        kmoy@google.com, ludloff@google.com, luto@kernel.org,
        nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com,
        tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver
Message-ID: <20200707032945.GA127977@linux.intel.com>
References: <20200617220844.57423-1-jarkko.sakkinen@linux.intel.com>
 <20200617220844.57423-12-jarkko.sakkinen@linux.intel.com>
 <20200627174335.GC15585@zn.tnic>
 <20200629152718.GA12312@linux.intel.com>
 <20200704014349.GB129411@linux.intel.com>
 <20200707013847.GA5208@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200707013847.GA5208@linux.intel.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Jul 06, 2020 at 06:38:47PM -0700, Sean Christopherson wrote:
> On Sat, Jul 04, 2020 at 04:43:49AM +0300, Jarkko Sakkinen wrote:
> > On Mon, Jun 29, 2020 at 08:27:19AM -0700, Sean Christopherson wrote:
> > > On Sat, Jun 27, 2020 at 07:43:35PM +0200, Borislav Petkov wrote:
> > > > And you could do similar sanity checks in the other ioctl functions.
> > > 
> > > Ya, as above, SGX_ENCL_INITIALIZED can be checked here.
> > > 
> > > SGX_ENCL_DEAD is actually already checked in in the top level sgx_ioctl(),
> > > i.e. the check in sgx_encl_add_page() can technically be flat out dropped.
> > > 
> > > I say "technically" because I'm a bit torn over SGX_ENCL_DEAD; encl->lock
> > > must be held to SGX_ENCL_DEAD (the page fault and reclaim flows rely on
> > > this), but as it stands today only ioctl() paths (guarded by SGX_ENCL_IOCTL)
> > > and sgx_release() (makes the ioctls() unreachable) set SGX_ENCL_DEAD.
> > > 
> > > So it's safe to check SGX_ENCL_DEAD from ioctl() context without holding
> > > encl->lock, at least in the current code base, but it feels weird/sketchy.
> > > 
> > > In the end I don't think I have a strong opinion.  Removing the technically
> > > unnecessary DEAD check in sgx_encl_add_page() is the simplest change, so it
> > > may make sense to do that and nothing more for initial upstreaming.  Long
> > > term, I fully expect we'll add paths that set SGX_ENCL_DEAD outside of
> > > ioctl() context, e.g. to handle EPC OOM, but it wouldn't be a bad thing to
> > > have a standalone commit in a future series to add DEAD checks (under
> > > encl->lock) in the ADD and INIT flows.
> > 
> > AFAIK nonne of th ioctl's should not need SGX_ENCL_DEAD check.
> 
> I can't tell if the double negative was intended, but I took a peek at your
> current master and see that you removed the SGX_ENCL_DEAD check in
> sgx_ioctl().  That check needs to stay, e.g. if EEXTEND fails we absolutely
> need to prevent any further operations on the enclave.
> 
> The above was calling out that additional checks on SGX_ENCL_DEAD after
> acquiring encl->lock are not necessary because SGX_ENCL_DEAD can only be
> set when the ioctls() are no longer reachable or from within an ioctl(),
> which provides exclusivity via SGX_ENCL_IOCTL.

Got it.

/Jarkko