From: "Haitao Huang" <haitao.huang@linux.intel.com>
To: "Reinette Chatre" <reinette.chatre@intel.com>,
"Jarkko Sakkinen" <jarkko@kernel.org>
Cc: "Andy Lutomirski" <luto@kernel.org>,
dave.hansen@linux.intel.com, tglx@linutronix.de, bp@alien8.de,
mingo@redhat.com, linux-sgx@vger.kernel.org, x86@kernel.org,
seanjc@google.com, kai.huang@intel.com, cathy.zhang@intel.com,
cedric.xing@intel.com, haitao.huang@intel.com,
mark.shanahan@intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/25] x86/sgx: Introduce runtime protection bits
Date: Fri, 07 Jan 2022 10:14:29 -0600 [thread overview]
Message-ID: <op.1fmvdehpwjvjmi@hhuan26-mobl1.mshome.net> (raw)
In-Reply-To: <YdgvFTIRboHwTgRT@iki.fi>
On Fri, 07 Jan 2022 06:16:21 -0600, Jarkko Sakkinen <jarkko@kernel.org>
wrote:
> On Thu, Jan 06, 2022 at 09:46:06AM -0800, Reinette Chatre wrote:
>> Hi Jarkko,
>>
>> On 12/28/2021 6:52 AM, Jarkko Sakkinen wrote:
>> > On Mon, Dec 13, 2021 at 02:10:17PM -0800, Reinette Chatre wrote:
>> >> Hi Jarkko,
>> >>
>> >> On 12/10/2021 11:42 PM, Jarkko Sakkinen wrote:
>> >>> 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?
>> >>
>> >> EMODPR and EMODPE are not equivalent.
>> >>
>> >> EMODPE can only be used to "extend"/relax permissions while EMODPR
>> can only
>> >> be used to restrict permissions.
>> >>
>> >> Notice in the EMODPE instruction reference of the SDM:
>> >>
>> >> (* Update EPCM permissions *)
>> >> EPCM(DS:RCX).R := EPCM(DS:RCX).R | SCRATCH_SECINFO.FLAGS.R;
>> >> EPCM(DS:RCX).W := EPCM(DS:RCX).W | SCRATCH_SECINFO.FLAGS.W;
>> >> EPCM(DS:RCX).X := EPCM(DS:RCX).X | SCRATCH_SECINFO.FLAGS.X;
>> >>
>> >> So, when using EMODPE it is only possible to add permissions, not
>> remove
>> >> permissions.
>> >>
>> >> If a user wants to remove permissions from an EPCM page it is only
>> possible
>> >> when using EMODPR. Notice in its instruction reference found in the
>> SDM how
>> >> it in turn can only be used to restrict permissions:
>> >>
>> >> (* Update EPCM permissions *)
>> >> EPCM(DS:RCX).R := EPCM(DS:RCX).R & SCRATCH_SECINFO.FLAGS.R;
>> >> EPCM(DS:RCX).W := EPCM(DS:RCX).W & SCRATCH_SECINFO.FLAGS.W;
>> >> EPCM(DS:RCX).X := EPCM(DS:RCX).X & SCRATCH_SECINFO.FLAGS.X;
>> >
>> > OK, so the question is: do we need both or would a mechanism just to
>> extend
>> > permissions be sufficient?
>>
>> I do believe that we need both in order to support pages having only
>> the permissions required to support their intended use during the time
>> the
>> particular access is required. While technically it is possible to grant
>> pages all permissions they may need during their lifetime it is safer to
>> remove permissions when no longer required.
>
> So if we imagine a run-time: how EMODPR would be useful, and how using it
> would make things safer?
>
In scenarios of JIT compilers, once code is generated into RW pages,
modifying both PTE and EPCM permissions to RX would be a good defensive
measure. In that case, EMODPR is useful.
Haitao
next prev parent reply other threads:[~2022-01-07 16:14 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 19:22 [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Reinette Chatre
2021-12-01 19:22 ` [PATCH 01/25] x86/sgx: Add shortlog descriptions to ENCLS wrappers Reinette Chatre
2021-12-04 18:30 ` Jarkko Sakkinen
2021-12-06 21:13 ` Reinette Chatre
2021-12-11 5:28 ` Jarkko Sakkinen
2021-12-13 22:06 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 02/25] x86/sgx: Add wrappers for SGX2 functions Reinette Chatre
2021-12-04 22:04 ` Jarkko Sakkinen
2021-12-06 21:15 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 03/25] x86/sgx: Support VMA permissions exceeding enclave permissions Reinette Chatre
2021-12-04 22:25 ` Jarkko Sakkinen
2021-12-04 22:27 ` Jarkko Sakkinen
2021-12-06 21:16 ` Reinette Chatre
2021-12-11 5:39 ` Jarkko Sakkinen
2021-12-13 22:08 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 04/25] x86/sgx: Add pfn_mkwrite() handler for present PTEs Reinette Chatre
2021-12-04 22:43 ` Jarkko Sakkinen
2021-12-06 21:18 ` Reinette Chatre
2021-12-11 7:37 ` Jarkko Sakkinen
2021-12-13 22:09 ` Reinette Chatre
2021-12-28 14:51 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 05/25] x86/sgx: Introduce runtime protection bits Reinette Chatre
2021-12-03 19:28 ` Andy Lutomirski
2021-12-03 22:12 ` Reinette Chatre
2021-12-04 0:38 ` Andy Lutomirski
2021-12-04 1:14 ` Reinette Chatre
2021-12-04 17:56 ` Andy Lutomirski
2021-12-04 23:55 ` Reinette Chatre
2021-12-13 22:34 ` Reinette Chatre
2021-12-04 23:57 ` Jarkko Sakkinen
2021-12-06 21:20 ` Reinette Chatre
2021-12-11 7:42 ` Jarkko Sakkinen
2021-12-13 22:10 ` Reinette Chatre
2021-12-28 14:52 ` Jarkko Sakkinen
2022-01-06 17:46 ` Reinette Chatre
2022-01-07 12:16 ` Jarkko Sakkinen
2022-01-07 16:14 ` Haitao Huang [this message]
2022-01-08 15:45 ` Jarkko Sakkinen
2022-01-08 15:51 ` Jarkko Sakkinen
2022-01-08 16:22 ` Jarkko Sakkinen
2022-01-10 22:05 ` Haitao Huang
2022-01-11 1:53 ` Jarkko Sakkinen
2022-01-11 1:55 ` Jarkko Sakkinen
2022-01-11 2:03 ` Jarkko Sakkinen
2022-01-11 2:15 ` Jarkko Sakkinen
2022-01-11 3:48 ` Haitao Huang
2022-01-12 23:48 ` Jarkko Sakkinen
2022-01-13 2:41 ` Haitao Huang
2022-01-14 21:36 ` Jarkko Sakkinen
2022-01-11 17:13 ` Reinette Chatre
2022-01-12 23:50 ` Jarkko Sakkinen
2022-01-12 23:56 ` Jarkko Sakkinen
2022-01-13 20:09 ` Nathaniel McCallum
2022-01-13 21:42 ` Reinette Chatre
2022-01-14 21:53 ` Jarkko Sakkinen
2022-01-14 21:57 ` Jarkko Sakkinen
2022-01-14 22:00 ` Jarkko Sakkinen
2022-01-14 22:17 ` Jarkko Sakkinen
2022-01-14 22:23 ` Jarkko Sakkinen
2022-01-14 22:34 ` Jarkko Sakkinen
2022-01-14 23:05 ` Reinette Chatre
2022-01-14 23:15 ` Jarkko Sakkinen
2022-01-15 0:01 ` Reinette Chatre
2022-01-15 0:27 ` Jarkko Sakkinen
2022-01-15 0:41 ` Reinette Chatre
2022-01-15 1:18 ` Jarkko Sakkinen
2022-01-15 11:56 ` Jarkko Sakkinen
2022-01-15 11:59 ` Jarkko Sakkinen
2022-01-17 13:13 ` Nathaniel McCallum
2022-01-18 1:59 ` Jarkko Sakkinen
2022-01-18 2:22 ` Jarkko Sakkinen
2022-01-18 3:31 ` Jarkko Sakkinen
2022-01-18 20:59 ` Reinette Chatre
2022-01-20 12:53 ` Jarkko Sakkinen
2022-01-20 16:52 ` Reinette Chatre
2022-01-26 14:41 ` Jarkko Sakkinen
2022-01-15 16:49 ` Jarkko Sakkinen
2022-01-18 21:18 ` Reinette Chatre
2022-01-17 13:27 ` Nathaniel McCallum
2022-01-18 21:11 ` Reinette Chatre
2021-12-04 22:50 ` Jarkko Sakkinen
2021-12-06 21:28 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 06/25] x86/sgx: Use more generic name for enclave cpumask function Reinette Chatre
2021-12-04 22:56 ` Jarkko Sakkinen
2021-12-06 21:29 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 07/25] x86/sgx: Move PTE zap code to separate function Reinette Chatre
2021-12-04 22:59 ` Jarkko Sakkinen
2021-12-06 21:30 ` Reinette Chatre
2021-12-11 7:52 ` Jarkko Sakkinen
2021-12-13 22:11 ` Reinette Chatre
2021-12-28 14:55 ` Jarkko Sakkinen
2022-01-06 17:46 ` Reinette Chatre
2022-01-07 12:26 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 08/25] x86/sgx: Make SGX IPI callback available internally Reinette Chatre
2021-12-04 23:00 ` Jarkko Sakkinen
2021-12-06 21:36 ` Reinette Chatre
2021-12-11 7:53 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 09/25] x86/sgx: Keep record of SGX page type Reinette Chatre
2021-12-04 23:03 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 10/25] x86/sgx: Support enclave page permission changes Reinette Chatre
2021-12-02 23:48 ` Dave Hansen
2021-12-03 18:18 ` Reinette Chatre
2021-12-03 0:32 ` Dave Hansen
2021-12-03 18:18 ` Reinette Chatre
2021-12-03 18:14 ` Dave Hansen
2021-12-03 18:49 ` Reinette Chatre
2021-12-03 19:38 ` Andy Lutomirski
2021-12-03 22:34 ` Reinette Chatre
2021-12-04 0:42 ` Andy Lutomirski
2021-12-04 1:35 ` Reinette Chatre
2021-12-04 23:08 ` Jarkko Sakkinen
2021-12-06 20:19 ` Dave Hansen
2021-12-11 5:17 ` Jarkko Sakkinen
2021-12-06 21:42 ` Reinette Chatre
2021-12-11 7:57 ` Jarkko Sakkinen
2021-12-13 22:12 ` Reinette Chatre
2021-12-28 14:56 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 11/25] selftests/sgx: Add test for EPCM " Reinette Chatre
2021-12-01 19:23 ` [PATCH 12/25] selftests/sgx: Add test for TCS page " Reinette Chatre
2021-12-01 19:23 ` [PATCH 13/25] x86/sgx: Support adding of pages to initialized enclave Reinette Chatre
2021-12-03 0:38 ` Dave Hansen
2021-12-03 18:47 ` Reinette Chatre
2021-12-04 23:13 ` Jarkko Sakkinen
2021-12-06 21:44 ` Reinette Chatre
2021-12-11 8:00 ` Jarkko Sakkinen
2021-12-13 22:12 ` Reinette Chatre
2021-12-28 14:57 ` Jarkko Sakkinen
2022-03-01 15:13 ` Jarkko Sakkinen
2022-03-01 17:08 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 14/25] x86/sgx: Tighten accessible memory range after enclave initialization Reinette Chatre
2021-12-04 23:14 ` Jarkko Sakkinen
2021-12-06 21:45 ` Reinette Chatre
2021-12-11 8:01 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 15/25] selftests/sgx: Test two different SGX2 EAUG flows Reinette Chatre
2021-12-01 19:23 ` [PATCH 16/25] x86/sgx: Support modifying SGX page type Reinette Chatre
2021-12-04 23:45 ` Jarkko Sakkinen
2021-12-06 21:48 ` Reinette Chatre
2021-12-11 8:02 ` Jarkko Sakkinen
2021-12-13 17:43 ` Dave Hansen
2021-12-21 8:52 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 17/25] x86/sgx: Support complete page removal Reinette Chatre
2021-12-04 23:45 ` Jarkko Sakkinen
2021-12-06 21:49 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 18/25] selftests/sgx: Introduce dynamic entry point Reinette Chatre
2021-12-01 19:23 ` [PATCH 19/25] selftests/sgx: Introduce TCS initialization enclave operation Reinette Chatre
2021-12-01 19:23 ` [PATCH 20/25] selftests/sgx: Test complete changing of page type flow Reinette Chatre
2021-12-01 19:23 ` [PATCH 21/25] selftests/sgx: Test faulty enclave behavior Reinette Chatre
2021-12-01 19:23 ` [PATCH 22/25] selftests/sgx: Test invalid access to removed enclave page Reinette Chatre
2021-12-01 19:23 ` [PATCH 23/25] selftests/sgx: Test reclaiming of untouched page Reinette Chatre
2021-12-01 19:23 ` [PATCH 24/25] x86/sgx: Free up EPC pages directly to support large page ranges Reinette Chatre
2021-12-04 23:47 ` Jarkko Sakkinen
2021-12-06 22:07 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 25/25] selftests/sgx: Page removal stress test Reinette Chatre
2021-12-02 18:30 ` [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Dave Hansen
2021-12-02 20:38 ` Nathaniel McCallum
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