linux-kernel - Re: [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2

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Date:   Thu, 2 Dec 2021 10:30:28 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        dave.hansen@...ux.intel.com, jarkko@...nel.org, tglx@...utronix.de,
        bp@...en8.de, luto@...nel.org, mingo@...hat.com,
        linux-sgx@...r.kernel.org, x86@...nel.org
Cc:     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 00/25] x86/sgx and selftests/sgx: Support SGX2

On 12/1/21 11:22 AM, Reinette Chatre wrote:
> * Support modifying permissions of regular enclave pages belonging to an
>   initialized enclave. New permissions are not allowed to exceed the
>   originally vetted permissions. Modifying permissions is accomplished
>   with a new ioctl SGX_IOC_PAGE_MODP.

It's probably also worth noting that this effectively punts on the issue
of how to allow enclaves to relax the permissions on pages, like taking
a page from R=>RW, or R=>RX.  RX isn't allowed unless the page was
*added* originally with RX or RWX.

Since dynamically added pages start with initial RW permissions, they
can *never* be RX or RWX since they did not start with execute
permissions.  That's a limitation, of course, but it's one that can be
dealt with separately from this set.

Does that sound sane to everyone?