linux-kernel - Re: [PATCH v5 06/11] intel_sgx: driver for Intel Software Guard Extensions

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Date:   Tue, 14 Nov 2017 22:12:25 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     James Morris <james.l.morris@...cle.com>
Cc:     intel-sgx-kernel-dev@...ts.01.org,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 06/11] intel_sgx: driver for Intel Software Guard
 Extensions

On Tue, Nov 14, 2017 at 10:41:50AM +1100, James Morris wrote:
> On Mon, 13 Nov 2017, Jarkko Sakkinen wrote:
> 
> > +
> > +	secs_epc = sgx_alloc_page(0);
> 
> Use SGX_ALLOC_ATOMIC instead of 0 ?

It is used in the #PF handler where it is not safe to swap pages in the
call context. I.e. you cannot lock mmap_sem without potentially causing
a deadlock.

> > +	if (IS_ERR(secs_epc)) {
> > +		ret = PTR_ERR(secs_epc);
> > +		goto out;
> > +	}
> 
> > +out:
> > +	if (encl)
> > +		kref_put(&encl->refcount, sgx_encl_release);
> > +	return ret;
> > +}
> 
> Don't you need an sgx_free_page() somewhere here?

It will get freed by sgx_encl_release().

> -- 
> James Morris
> <james.l.morris@...cle.com>

/Jarkko