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From: Jarkko Sakkinen <jarkko@kernel.org>
To: x86@kernel.org, linux-sgx@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Jethro Beekman <jethro@fortanix.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Jarkko Sakkinen <jarkko@kernel.org>,
	andriy.shevchenko@linux.intel.com, asapek@google.com,
	bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com,
	conradparker@google.com, cyhanish@google.com,
	haitao.huang@intel.com, kai.huang@intel.com, kai.svahn@intel.com,
	kmoy@google.com, ludloff@google.com, luto@kernel.org,
	nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com,
	rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com,
	mikko.ylinen@intel.com
Subject: [PATCH v41 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct
Date: Fri, 13 Nov 2020 00:01:21 +0200
Message-ID: <20201112220135.165028-11-jarkko@kernel.org> (raw)
In-Reply-To: <20201112220135.165028-1-jarkko@kernel.org>

From: Sean Christopherson <sean.j.christopherson@intel.com>

Background
==========

1. SGX enclave pages are populated with data by copying from normal memory
   via ioctl() (SGX_IOC_ENCLAVE_ADD_PAGES), which will be added later in
   this series.
2. It is desirable to be able to restrict those normal memory data sources.
   For instance, to ensure that the source data is executable before
   copying data to an executable enclave page.
3. Enclave page permissions are dynamic (just like normal permissions) and
   can be adjusted at runtime with mprotect().

This creates a problem because the original data source may have long since
vanished at the time when enclave page permissions are established (mmap()
or mprotect()).

The solution (elsewhere in this series) is to force enclaves creators to
declare their paging permission *intent* up front to the ioctl().  This
intent can be immediately compared to the source data’s mapping and
rejected if necessary.

The “intent” is also stashed off for later comparison with enclave
PTEs. This ensures that any future mmap()/mprotect() operations
performed by the enclave creator or done on behalf of the enclave
can be compared with the earlier declared permissions.

Problem
=======

There is an existing mmap() hook which allows SGX to perform this
permission comparison at mmap() time.  However, there is no corresponding
->mprotect() hook.

Solution
========

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.

Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Jethro Beekman <jethro@fortanix.com> # v40
Acked-by: Dave Hansen <dave.hansen@intel.com> # v40
# Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
Changes from v40:
* Move mprotect_fixup() outside of the callback. This keeps mm internals
  outside of the callback.

 include/linux/mm.h | 7 +++++++
 mm/mprotect.c      | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index db6ae4d3fb4e..1813fa86b981 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -559,6 +559,13 @@ struct vm_operations_struct {
 	void (*close)(struct vm_area_struct * area);
 	int (*split)(struct vm_area_struct * area, unsigned long addr);
 	int (*mremap)(struct vm_area_struct * area);
+	/*
+	 * Called by mprotect() to make driver-specific permission
+	 * checks before mprotect() is finalised.   The VMA must not
+	 * be modified.  Returns 0 if eprotect() can proceed.
+	 */
+	int (*mprotect)(struct vm_area_struct *vma, unsigned long start,
+			unsigned long end, unsigned long newflags);
 	vm_fault_t (*fault)(struct vm_fault *vmf);
 	vm_fault_t (*huge_fault)(struct vm_fault *vmf,
 			enum page_entry_size pe_size);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 56c02beb6041..ab709023e9aa 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -616,9 +616,16 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		tmp = vma->vm_end;
 		if (tmp > end)
 			tmp = end;
+
+		if (vma->vm_ops && vma->vm_ops->mprotect)
+			error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
+		if (error)
+			goto out;
+
 		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 		if (error)
 			goto out;
+
 		nstart = tmp;
 
 		if (nstart < prev->vm_end)
-- 
2.27.0


  parent reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12 22:01 [PATCH v41 00/24] Intel SGX foundations Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 01/24] x86/sgx: Add SGX architectural data structures Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 02/24] x86/sgx: Add wrappers for ENCLS functions Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 03/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 04/24] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control " Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 05/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Jarkko Sakkinen
2020-11-16 22:25   ` [PATCH] x86/sgx: clarify 'laundry_list' locking Dave Hansen
2020-11-17 19:29     ` Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 06/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 07/24] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 08/24] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 09/24] x86/sgx: Add SGX page allocator functions Jarkko Sakkinen
2020-11-12 22:01 ` Jarkko Sakkinen [this message]
2020-11-13 10:25   ` [PATCH v41 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct Mel Gorman
2020-11-17 18:16     ` Jarkko Sakkinen
2020-11-15 17:08   ` Dr. Greg
2020-11-15 17:32   ` Matthew Wilcox
2020-11-15 18:36     ` Dave Hansen
2020-11-16 10:09       ` Mel Gorman
2020-11-17 19:15         ` Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 11/24] x86/sgx: Add SGX misc driver interface Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE Jarkko Sakkinen
     [not found]   ` <20201115044044.11040-1-hdanton@sina.com>
2020-11-17 17:35     ` Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 15/24] x86/sgx: Add SGX_IOC_ENCLAVE_PROVISION Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 16/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 17/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 18/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 19/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-11-17 13:14   ` Borislav Petkov
2020-11-17 19:41     ` Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 20/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-11-16 18:19   ` Shuah Khan
2020-11-17 13:22     ` Borislav Petkov
2020-11-17 19:42     ` Jarkko Sakkinen
2020-11-17 17:26   ` Borislav Petkov
2020-11-17 21:27     ` Jarkko Sakkinen
2020-11-17 21:38     ` Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 21/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 22/24] x86/sgx: Add ptrace() support for the SGX driver Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 23/24] docs: x86/sgx: Document SGX kernel architecture Jarkko Sakkinen
2020-11-12 22:01 ` [PATCH v41 24/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2020-11-16 16:55 ` [PATCH v41 00/24] Intel SGX foundations Borislav Petkov
2020-11-16 17:21   ` Dave Hansen
2020-11-16 17:28     ` Borislav Petkov
2020-11-17 19:20       ` Jarkko Sakkinen
     [not found] ` <20201114084211.5284-1-hdanton@sina.com>
2020-11-16 18:33   ` [PATCH v41 05/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Dave Hansen
     [not found] ` <20201115040127.7804-1-hdanton@sina.com>
2020-11-16 21:11   ` [PATCH v41 11/24] x86/sgx: Add SGX misc driver interface Dave Hansen
     [not found] ` <20201114090708.8684-1-hdanton@sina.com>
2020-11-17 18:12   ` [PATCH v41 06/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
     [not found] ` <20201114093256.7800-1-hdanton@sina.com>
2020-11-17 18:14   ` [PATCH v41 09/24] x86/sgx: Add SGX page allocator functions Jarkko Sakkinen
     [not found] ` <20201115030548.1572-1-hdanton@sina.com>
2020-11-17 18:22   ` [PATCH v41 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct Jarkko Sakkinen
2020-12-15  5:38 ` [PATCH v41 00/24] Intel SGX foundations Hui, Chunyang
2020-12-15  5:43 ` Hui, Chunyang
2020-12-15 15:58   ` Jarkko Sakkinen

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