linux-kernel - Re: [PATCH 05/25] x86/sgx: Introduce runtime protection bits

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Date:   Sat, 11 Dec 2021 09:42:11 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     dave.hansen@...ux.intel.com, tglx@...utronix.de, bp@...en8.de,
        mingo@...hat.com, linux-sgx@...r.kernel.org, x86@...nel.org,
        seanjc@...gle.com, kai.huang@...el.com, cathy.zhang@...el.com,
        cedric.xing@...el.com, haitao.huang@...el.com,
        mark.shanahan@...el.com, hpa@...or.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/25] x86/sgx: Introduce runtime protection bits

On Mon, 2021-12-06 at 13:20 -0800, Reinette Chatre wrote:
> > This is a valid question. Since EMODPE exists why not just make things for
> > EMODPE, and ignore EMODPR altogether?
> > 
> 
> I believe that we should support the best practice of principle of least 
> privilege - once a page no longer needs a particular permission there 
> should be a way to remove it (the unneeded permission).

What if EMODPR was not used at all, since EMODPE is there anyway?

This could be achieved e.g. by having ioctl to change protection
bits in encl->page_tree.

This would simplify things a lot given that there would be only
two, instead of three, EACCEPT code paths.

/Jarkko