From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Haitao Huang <haitao.huang@linux.intel.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
Jethro Beekman <jethro@fortanix.com>,
Darren Kenny <darren.kenny@oracle.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
asapek@google.com, Borislav Petkov <bp@alien8.de>,
"Xing, Cedric" <cedric.xing@intel.com>,
chenalexchen@google.com, Conrad Parker <conradparker@google.com>,
cyhanish@google.com, "Huang, Haitao" <haitao.huang@intel.com>,
Josh Triplett <josh@joshtriplett.org>,
"Huang, Kai" <kai.huang@intel.com>,
"Svahn, Kai" <kai.svahn@intel.com>, Keith Moyer <kmoy@google.com>,
Christian Ludloff <ludloff@google.com>,
Neil Horman <nhorman@redhat.com>,
Nathaniel McCallum <npmccallum@redhat.com>,
Patrick Uiterwijk <puiterwijk@redhat.com>,
David Rientjes <rientjes@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
yaozhangx@google.com
Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()
Date: Fri, 25 Sep 2020 12:43:04 -0700 [thread overview]
Message-ID: <20200925194304.GE31528@linux.intel.com> (raw)
In-Reply-To: <32fc9df4-d4aa-6768-aa06-0035427b7535@intel.com>
On Fri, Sep 25, 2020 at 10:18:28AM -0700, Dave Hansen wrote:
> Thanks for the walkthrough. The thing that clicked for me seeing those
> examples was how the earlier ioctl(ADD_PAGE) is "bound" to later
> enforcement actions at enclave PTE creation time.
>
> On 9/24/20 5:00 PM, Sean Christopherson wrote:
> > My concern is that if we merge this
> >
> > ioctl(sgx_fd, ENCLAVE_ADD_PAGE, SGX_PROT_READ | SGX_PROT_EXEC, ptr, size);
> >
> > without ->mprotect(), we can't actually enforce the declared protections. And
> > if we drop the field altogether:
> >
> > ioctl(sgx_fd, ENCLAVE_ADD_PAGE, ptr, size);
> >
> > then we can't implement security_enclave_load().
>
> To me, it's perfectly OK to have parts of the ABI which are unused. It
> sure makes them harder to test if there are no actual users in the code,
> but if it solves a real problem with the ABI, I'm fine with it.
>
> Let's see if I can put all the pieces together.
>
> Background:
>
> 1. SGX enclave pages are populated with data by copying data to them
> from normal memory via: ioctl(sgx_fd, ENCLAVE_ADD_PAGE, src_ptr...);
> 2. We want to be able to restrict those normal memory data sources. For
> instance, before copying data to an executable enclave page, we might
> ensure that the source is executable.
> 3. Enclave page permissions are dynamic just like normal permissions and
> can be adjusted at runtime with mprotect() (along with a
> corresponding special instruction inside the enclave)
> 4. The original data source may have have long since vanished at the
> time when enclave page permission are established (mmap() or
> mprotect())
>
> Solution:
>
> The solution is to force enclaves creators to declare their intent up
> front to ioctl(ENCLAVE_ADD_PAGE). This intent can me immediately
> compared to the source data mapping (and rejected if necessary). It is
> also stashed off and then later compared with enclave PTEs to ensure
> that any future mmap()/mprotect() operations performed by the enclave
> creator or the enclave itself are consistent with the earlier declared
> permissions.
>
> Essentially, this means that whenever the kernel is asked to change an
> enclave PTE, it needs to ensure the change is consistent with that
> stashed intent. There is an existing vm_ops->mmap() hook which allows
> SGX to do that for mmap(). However, there is no ->mprotect() hook. Add
> a vm_ops->mprotect() hook so that mprotect() operations which are
> inconsistent with any page's stashed intent can be rejected by the driver.
Yes to all of the above.
> Implications:
>
> However, there is currently no implementation of the intent checks at
> the time of ioctl(ENCLAVE_ADD_PAGE).
Correct.
> That means that the intent argument (SGX_PROT_*) is currently unused.
No, the intent argument is used (eventually) by SGX's ->mprotect()
implementation, i.e. sgx_mprotect() enforces that the actual protections are a
subset of the declared/intended protections.
If ->mprotect() is not merged, then it yes, it will be unused. And therein
lies the problem as the kernel can't start using/enforcing the intent without
breaking userspace. E.g. an enclave loaded with SGX_PROT_READ but mprotect()'d
with PROT_READ | PROT_EXEC would break if sgx_mprotect() came along.
One way to avoid introducing ->mprotect() would be to require all enclaves to
declare all pages with READ|WRITE|EXEC. Then we could drop sgx_mprotect()
since the mprotect() permissions are guaranteed to be a subset of the declared
permissions. That would have the added bonus of eliminating the per-page
checks in sgx_mmap()/sgx_mprotect(), though I've no idea if that is a
meaningful optmization or it's lost in the noise.
The big downside of requiring READ|WRITE|EXEC is that it will make life hell
for a LSM policy owner if they ever want to apply EXECMEM or EXECMOD style
restritions on enclaves, i.e. if SELinux folks want to add
security_enclave_load().
I find that I'm more or less ok with that approach, in no small part because
introducing security_enclave_load() might be a pretty big "if", e.g. security
folks may decide that they'd rather allow/deny enclaves based on the
measurement or signer of the enclave and eschew per-page checks entirely.
> --
>
> Is that all correct? Did I miss anything?
next prev parent reply other threads:[~2020-09-25 22:45 UTC|newest]
Thread overview: 182+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 11:28 [PATCH v38 00/24] Intel SGX foundations Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 02/24] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control " Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-09-16 11:44 ` Borislav Petkov
2020-09-16 20:30 ` Jarkko Sakkinen
2020-09-16 20:32 ` Borislav Petkov
2020-09-15 11:28 ` [PATCH v38 04/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 05/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 06/24] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 07/24] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 08/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 09/24] x86/sgx: Add __sgx_alloc_epc_page() and sgx_free_epc_page() Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Jarkko Sakkinen
2020-09-18 12:44 ` Borislav Petkov
2020-09-18 15:09 ` Andy Lutomirski
2020-09-18 23:24 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect()' Jarkko Sakkinen
2020-09-18 23:53 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Sean Christopherson
2020-09-19 0:15 ` Andy Lutomirski
[not found] ` <20200922125801.GA133710@linux.intel.com>
2020-09-22 15:11 ` Dave Hansen
2020-09-23 13:30 ` Jarkko Sakkinen
2020-09-23 13:43 ` Jarkko Sakkinen
2020-09-23 14:33 ` Jarkko Sakkinen
2020-09-24 14:50 ` Dave Hansen
2020-09-24 16:27 ` Sean Christopherson
[not found] ` <20200921124946.GF6038@linux.intel.com>
2020-09-21 12:51 ` Jarkko Sakkinen
2020-09-21 13:14 ` Jarkko Sakkinen
[not found] ` <20200921165758.GA24156@linux.intel.com>
2020-09-21 21:07 ` Jarkko Sakkinen
2020-09-21 21:18 ` Sean Christopherson
2020-09-22 5:29 ` Jarkko Sakkinen
2020-09-22 5:35 ` Jarkko Sakkinen
2020-09-22 16:43 ` Sean Christopherson
2020-09-23 13:50 ` Jarkko Sakkinen
2020-09-24 19:11 ` Haitao Huang
2020-09-24 19:28 ` Sean Christopherson
2020-09-24 19:39 ` Dave Hansen
2020-09-24 20:01 ` Sean Christopherson
2020-09-24 20:10 ` Dave Hansen
2020-09-24 20:25 ` Sean Christopherson
2020-09-24 20:54 ` Dave Hansen
2020-09-24 23:05 ` Sean Christopherson
2020-09-24 23:09 ` Dave Hansen
2020-09-25 0:00 ` Sean Christopherson
2020-09-25 17:18 ` Dave Hansen
2020-09-25 19:43 ` Sean Christopherson [this message]
2020-09-25 19:53 ` Dave Hansen
2020-09-26 4:15 ` Andy Lutomirski
2020-09-28 0:53 ` Jarkko Sakkinen
2020-09-28 14:04 ` Dave Hansen
2020-09-28 16:19 ` Jarkko Sakkinen
2020-09-28 16:48 ` Dave Hansen
2020-09-28 19:32 ` Jarkko Sakkinen
2020-09-28 19:45 ` Dave Hansen
2020-09-28 20:19 ` Jarkko Sakkinen
2020-09-29 1:37 ` Andy Lutomirski
2020-09-29 4:05 ` Jarkko Sakkinen
2020-09-29 14:24 ` Dave Hansen
2020-09-30 0:20 ` Jarkko Sakkinen
2020-09-30 14:35 ` Dave Hansen
2020-09-28 20:18 ` Jarkko Sakkinen
2020-10-18 8:49 ` Dr. Greg
2020-10-19 21:31 ` Sean Christopherson
2020-10-20 10:01 ` Dr. Greg
2020-10-20 16:40 ` Sean Christopherson
2020-10-24 14:37 ` Dr. Greg
2020-10-24 15:33 ` Andy Lutomirski
2020-10-26 10:51 ` Dr. Greg
2020-10-26 22:59 ` Andy Lutomirski
2020-10-27 0:40 ` Sean Christopherson
2020-09-24 22:07 ` Jarkko Sakkinen
2020-09-24 21:58 ` Jarkko Sakkinen
2020-09-24 21:55 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 11/24] x86/sgx: Add SGX enclave driver Jarkko Sakkinen
2020-09-21 9:30 ` Borislav Petkov
2020-09-21 12:09 ` Jarkko Sakkinen
2020-10-01 17:36 ` Sean Christopherson
2020-10-01 18:49 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE Jarkko Sakkinen
2020-09-21 10:03 ` Borislav Petkov
2020-09-21 12:28 ` Jarkko Sakkinen
2020-09-21 13:51 ` Borislav Petkov
2020-09-21 19:29 ` Jarkko Sakkinen
2020-10-03 0:23 ` Haitao Huang
2020-10-03 3:24 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT Jarkko Sakkinen
2020-09-21 17:35 ` Borislav Petkov
2020-09-21 18:10 ` Sean Christopherson
2020-09-21 18:27 ` Borislav Petkov
[not found] ` <20200921191658.GA24823@linux.intel.com>
2020-09-22 8:29 ` Borislav Petkov
2020-09-22 11:50 ` Jarkko Sakkinen
2020-09-22 12:56 ` Jethro Beekman
2020-09-22 14:29 ` Borislav Petkov
2020-09-23 14:47 ` Jarkko Sakkinen
2020-09-23 15:55 ` Borislav Petkov
2020-09-24 12:23 ` Jarkko Sakkinen
2020-09-22 16:29 ` Sean Christopherson
2020-09-21 19:22 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 15/24] x86/sgx: Enable provisioning for remote attestation Jarkko Sakkinen
2020-09-21 18:07 ` Borislav Petkov
2020-09-21 19:27 ` Jarkko Sakkinen
2020-09-21 19:41 ` Borislav Petkov
2020-09-21 21:26 ` Jarkko Sakkinen
2020-09-22 8:30 ` Borislav Petkov
2020-09-15 11:28 ` [PATCH v38 16/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-09-22 10:45 ` Borislav Petkov
2020-09-22 14:03 ` Jarkko Sakkinen
2020-09-22 14:24 ` Borislav Petkov
2020-09-23 14:52 ` Jarkko Sakkinen
2020-09-29 1:14 ` Sean Christopherson
2020-09-29 3:50 ` Jarkko Sakkinen
2020-09-29 8:35 ` Sean Christopherson
2020-09-22 16:24 ` Sean Christopherson
2020-09-22 18:02 ` Borislav Petkov
2020-09-23 15:25 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 17/24] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2020-09-22 15:44 ` Borislav Petkov
2020-09-23 13:20 ` Jarkko Sakkinen
2020-09-23 16:17 ` Borislav Petkov
2020-09-24 11:51 ` Jarkko Sakkinen
2020-09-24 15:57 ` Borislav Petkov
2020-09-24 20:38 ` [PATCH v38 17/24] x86/sgx: ptrace() support for the SGX driver' Jarkko Sakkinen
2020-09-24 20:40 ` Jarkko Sakkinen
2020-09-25 7:53 ` Borislav Petkov
2020-09-25 11:00 ` Jarkko Sakkinen
2020-09-25 7:51 ` Borislav Petkov
2020-09-25 11:21 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 18/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-09-23 22:07 ` Borislav Petkov
2020-09-24 12:09 ` Jarkko Sakkinen
2020-09-24 16:00 ` Borislav Petkov
2020-09-24 21:07 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 19/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 20/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2020-09-24 16:31 ` Borislav Petkov
2020-09-24 23:11 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-09-24 18:04 ` Borislav Petkov
2020-09-25 1:00 ` Jarkko Sakkinen
2020-09-25 8:28 ` Borislav Petkov
2020-09-27 23:37 ` Jarkko Sakkinen
2020-09-28 8:30 ` Borislav Petkov
2020-09-28 15:02 ` Jarkko Sakkinen
2020-09-25 8:39 ` Jethro Beekman
2020-09-25 11:17 ` Jarkko Sakkinen
2020-09-25 11:43 ` Jethro Beekman
[not found] ` <20200925003808.GB20333@linux.intel.com>
2020-09-25 1:04 ` Jarkko Sakkinen
2020-09-25 8:14 ` Borislav Petkov
2020-09-25 10:59 ` Jarkko Sakkinen
2020-09-28 14:36 ` Jarkko Sakkinen
2020-09-25 18:23 ` Andrew Cooper
2020-09-28 0:58 ` Jarkko Sakkinen
2020-09-28 16:44 ` Andrew Cooper
2020-09-28 18:07 ` H.J. Lu
2020-09-28 18:12 ` Andy Lutomirski
2020-09-28 18:17 ` Dave Hansen
2020-09-28 22:07 ` Jarkko Sakkinen
2020-09-28 21:56 ` Jarkko Sakkinen
2020-09-28 22:06 ` H.J. Lu
2020-09-28 22:18 ` Dave Hansen
2020-09-28 22:41 ` Andy Lutomirski
2020-09-28 23:38 ` Andrew Cooper
2020-09-29 14:10 ` Dave Hansen
2020-09-29 15:01 ` Andrew Cooper
2020-09-28 21:41 ` Jarkko Sakkinen
2020-09-28 20:42 ` Jarkko Sakkinen
2020-09-28 23:52 ` Andrew Cooper
2020-09-30 0:52 ` Jarkko Sakkinen
2020-09-28 15:43 ` Yu, Yu-cheng
2020-09-28 15:54 ` H.J. Lu
2020-09-28 16:40 ` Yu, Yu-cheng
2020-09-28 21:36 ` Jarkko Sakkinen
2020-09-28 20:56 ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 22/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 23/24] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-09-23 13:50 ` Borislav Petkov
2020-09-24 11:28 ` Jarkko Sakkinen
2020-09-24 15:54 ` Borislav Petkov
2020-09-15 11:28 ` [PATCH v38 24/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2020-09-25 22:37 ` Sean Christopherson
2020-09-28 0:44 ` Jarkko Sakkinen
-- strict thread matches above, loose matches on Subject: below --
2020-09-15 11:04 [PATCH v38 00/24] Intel SGX foundations Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Jarkko Sakkinen
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