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

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Date:   Sat, 4 Jul 2020 06:31:10 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Haitao Huang <haitao.huang@...ux.intel.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, haitao.huang@...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, 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;

/Jarkko