linux-kernel - Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

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Date:   Fri, 14 Feb 2020 09:40:00 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jethro Beekman <jethro@...tanix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, nhorman@...hat.com, npmccallum@...hat.com,
        haitao.huang@...el.com, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kai.svahn@...el.com, bp@...en8.de,
        josh@...htriplett.org, luto@...nel.org, kai.huang@...el.com,
        rientjes@...gle.com, cedric.xing@...el.com, puiterwijk@...hat.com,
        linux-security-module@...r.kernel.org,
        Haitao Huang <haitao.huang@...ux.intel.com>
Subject: Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver



> On Feb 14, 2020, at 9:11 AM, Sean Christopherson <sean.j.christopherson@...el.com> wrote:
> 
> On Fri, Feb 14, 2020 at 10:24:10AM +0100, Jethro Beekman wrote:
>>> On 2020-02-13 19:07, Sean Christopherson wrote:
>>> On Thu, Feb 13, 2020 at 02:59:52PM +0100, Jethro Beekman wrote:
>>>> On 2020-02-09 22:25, Jarkko Sakkinen wrote:
>>>>> +/**
>>>>> + * struct sgx_enclave_add_pages - parameter structure for the
>>>>> + *                                %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
>>>>> + * @src:    start address for the page data
>>>>> + * @offset:    starting page offset
>>>>> + * @length:    length of the data (multiple of the page size)
>>>>> + * @secinfo:    address for the SECINFO data
>>>>> + * @flags:    page control flags
>>>>> + * @count:    number of bytes added (multiple of the page size)
>>>>> + */
>>>>> +struct sgx_enclave_add_pages {
>>>>> +    __u64    src;
>>>>> +    __u64    offset;
>>>>> +    __u64    length;
>>>>> +    __u64    secinfo;
>>>>> +    __u64    flags;
>>>>> +    __u64    count;
>>>>> +};
>>>> 
>>>> Compared to the last time I looked at the patch set, this API removes the
>>>> ability to measure individual pages chunks. That is not acceptable.
>>> 
>>> Why is it not acceptable?  E.g. what specific use case do you have that
>>> _requires_ on measuring partial 4k pages of an enclave?
>> 
>> The use case is someone gives me an enclave and I want to load it. If I don't
>> load it exactly as the enclave author specified, the enclave hash will be
>> different, and it won't work.
> 
> And if our ABI says "thou shall measure in 4k chunks", then it's an invalid
> enclave if its author generated MRENCLAVE using a different granularity.

ISTM, unless there’s a particularly compelling reason, if an enclave is valid, we should be able to load it.