linux-kernel - Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver

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Date:   Wed, 02 Sep 2020 13:40:47 -0500
From:   "Haitao Huang" <haitao.huang@...ux.intel.com>
To:     "Sean Christopherson" <sean.j.christopherson@...el.com>
Cc:     "Jarkko Sakkinen" <jarkko.sakkinen@...ux.intel.com>,
        x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        "Jethro Beekman" <jethro@...tanix.com>,
        "Chunyang Hui" <sanqian.hcy@...fin.com>,
        "Jordan Hand" <jorhand@...ux.microsoft.com>,
        "Nathaniel McCallum" <npmccallum@...hat.com>,
        "Seth Moore" <sethmo@...gle.com>,
        "Suresh Siddha" <suresh.b.siddha@...el.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, bp@...en8.de, cedric.xing@...el.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, josh@...htriplett.org,
        kai.huang@...el.com, kai.svahn@...el.com, kmoy@...gle.com,
        ludloff@...gle.com, luto@...nel.org, nhorman@...hat.com,
        puiterwijk@...hat.com, rientjes@...gle.com, tglx@...utronix.de,
        yaozhangx@...gle.com
Subject: Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver

On Wed, 02 Sep 2020 11:10:12 -0500, Sean Christopherson  
<sean.j.christopherson@...el.com> wrote:

> On Tue, Sep 01, 2020 at 10:06:32PM -0500, Haitao Huang wrote:
>> On Fri, 03 Jul 2020 22:31:10 -0500, Jarkko Sakkinen
>> <jarkko.sakkinen@...ux.intel.com> wrote:
>>
>> > On Wed, Jul 01, 2020 at 08:59:02PM -0700, Sean Christopherson wrote:
>> > > On Thu, Jun 18, 2020 at 01:08:33AM +0300, Jarkko Sakkinen wrote:
>> > > > +static int sgx_validate_secs(const struct sgx_secs *secs,
>> > > > +			     unsigned long ssaframesize)
>> > > > +{
>> > > > +	if (secs->size < (2 * PAGE_SIZE) || !is_power_of_2(secs->size))
>> > > > +		return -EINVAL;
>> > > > +
>> > > > +	if (secs->base & (secs->size - 1))
>> > > > +		return -EINVAL;
>> > > > +
>> > > > +	if (secs->miscselect & sgx_misc_reserved_mask ||
>> > > > +	    secs->attributes & sgx_attributes_reserved_mask ||
>> > > > +	    secs->xfrm & sgx_xfrm_reserved_mask)
>> > > > +		return -EINVAL;
>> > > > +
>> > > > +	if (secs->attributes & SGX_ATTR_MODE64BIT) {
>> > > > +		if (secs->size > sgx_encl_size_max_64)
>> > > > +			return -EINVAL;
>> > > > +	} else if (secs->size > sgx_encl_size_max_32)
>> > > > +		return -EINVAL;
>> > >
>> > > These should be >=, not >, the SDM uses one of those fancy ≥  
>> ligatures.
>> > >
>> > > Internal versions use more obvious pseudocode, e.g.:
>> > >
>> > >     if ((DS:TMP_SECS.ATTRIBUTES.MODE64BIT = 1) AND
>> > >         (DS:TMP_SECS.SIZE AND (~((1 << CPUID.18.0:EDX[15:8]) – 1)))
>> > >     {
>> > >         #GP(0);
>> >
>> > Updated as:
>> >
>> > static int sgx_validate_secs(const struct sgx_secs *secs)
>> > {
>> > 	u64 max_size = (secs->attributes & SGX_ATTR_MODE64BIT) ?
>> > 		       sgx_encl_size_max_64 : sgx_encl_size_max_32;
>> >
>> > 	if (secs->size < (2 * PAGE_SIZE) || !is_power_of_2(secs->size))
>> > 		return -EINVAL;
>> >
>> > 	if (secs->base & (secs->size - 1))
>> > 		return -EINVAL;
>> >
>> > 	if (secs->miscselect & sgx_misc_reserved_mask ||
>> > 	    secs->attributes & sgx_attributes_reserved_mask ||
>> > 	    secs->xfrm & sgx_xfrm_reserved_mask)
>> > 		return -EINVAL;
>> >
>> > 	if (secs->size >= max_size)
>> > 		return -EINVAL;
>> >
>>
>> This should be > not >=. Issue raised and fixed by Fábio Silva for  
>> ported
>> patches for OOT SGX support:
>> https://github.com/intel/SGXDataCenterAttestationPrimitives/pull/123
>>
>> I tested and verified with Intel arch, the comparison indeed should be  
>> >.
>
> And this is a confirmed SDM bug, correct?

yes, the pseudo code for ECREATE is inaccurate and inconsistent with the  
CPUID spec. The latter is correct.
Haitao