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From: Andy Lutomirski <luto@amacapital.net>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	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, Dave Hansen <dave.hansen@intel.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, 18 Sep 2020 17:15:32 -0700
Message-ID: <1B23E216-0229-4BDD-8B09-807256A54AF5@amacapital.net> (raw)
In-Reply-To: <20200918235337.GA21189@sjchrist-ice>


> On Sep 18, 2020, at 4:53 PM, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
> 
> On Fri, Sep 18, 2020 at 08:09:04AM -0700, Andy Lutomirski wrote:
>>> On Tue, Sep 15, 2020 at 4:28 AM Jarkko Sakkinen
>>> <jarkko.sakkinen@linux.intel.com> wrote:
>>> 
>>> From: Sean Christopherson <sean.j.christopherson@intel.com>
>>> 
>>> Add vm_ops()->mprotect() for additional constraints for a VMA.
>>> 
>>> Intel Software Guard eXtensions (SGX) will use this callback to add two
>>> constraints:
>>> 
>>> 1. Verify that the address range does not have holes: each page address
>>>   must be filled with an enclave page.
>>> 2. Verify that VMA permissions won't surpass the permissions of any enclave
>>>   page within the address range. Enclave cryptographically sealed
>>>   permissions for each page address that set the upper limit for possible
>>>   VMA permissions. Not respecting this can cause #GP's to be emitted.
> 
> Side note, #GP is wrong.  EPCM violations are #PFs.  Skylake CPUs #GP, but
> that's technically an errata.  But this isn't the real motivation, e.g.
> userspace can already trigger #GP/#PF by reading/writing a bad address, SGX
> simply adds another flavor.
> 
>> It's been awhile since I looked at this.  Can you remind us: is this
>> just preventing userspace from shooting itself in the foot or is this
>> something more important?
> 
> Something more important, it's used to prevent userspace from circumventing
> a noexec filesystem by loading code into an enclave, and to give the kernel the
> option of adding enclave specific LSM policies in the future.
> 
> The source file (if one exists) for the enclave is long gone when the enclave
> is actually mmap()'d and mprotect()'d.  To enforce noexec, the requested
> permissions for a given page are snapshotted when the page is added to the
> enclave, i.e. when the enclave is built.  Enclave pages that will be executable
> must originate from an a MAYEXEC VMA, e.g. the source page can't come from a
> noexec file system.
> 
> The ->mprotect() hook allows SGX to reject mprotect() if userspace is declaring
> permissions beyond what are allowed, e.g. trying to map an enclave page with
> EXEC permissions when the page was added to the enclave without EXEC.
> 
> Future LSM policies have a similar need due to vm_file always pointing at
> /dev/sgx/enclave, e.g. policies couldn't be attached to a specific enclave.
> ->mprotect() again allows enforcing permissions at map time that were checked
> at enclave build time, e.g. via an LSM hook.
> 
> Deferring ->mprotect() until LSM support is added (if it ever is) would be
> problematic due to SGX2.  With SGX2, userspace can extend permissions of an
> enclave page (for the CPU's EPC Map entry, not the kernel's page tables)
> without bouncing through the kernel.  Without ->mprotect () enforcement.
> userspace could do EADD(RW) -> mprotect(RWX) -> EMODPE(X) to gain W+X.  We
> want to disallow such a flow now, i.e. force userspace to do EADD(RW,X), so
> that the hypothetical LSM hook would have all information at EADD(), i.e.
> would be aware of the EXEC permission, without creating divergent behavior
> based on whether or not an LSM is active.

That’s what I thought. Can we get this in the changelog?

  reply index

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 [this message]
     [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
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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