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Date: Tue, 21 Jun 2016 17:47:06 -0700
From: Kees Cook <keescook@...omium.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
Thomas Garnier <thgarnie@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
x86@...nel.org,
Borislav Petkov <bp@...e.de>,
Baoquan He <bhe@...hat.com>,
Yinghai Lu <yinghai@...nel.org>,
Juergen Gross <jgross@...e.com>,
Matt Fleming <matt@...eblueprint.co.uk>,
Toshi Kani <toshi.kani@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Alexander Kuleshov <kuleshovmail@...il.com>,
Alexander Popov <alpopov@...ecurity.com>,
Dave Young <dyoung@...hat.com>,
Joerg Roedel <jroedel@...e.de>,
Lv Zheng <lv.zheng@...el.com>,
Mark Salter <msalter@...hat.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Jan Beulich <JBeulich@...e.com>,
linux-kernel@...r.kernel.org,
Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH v7 9/9] x86/mm: Memory hotplug support for KASLR memory randomization (x86_64)
From: Thomas Garnier <thgarnie@...gle.com>
Add a new option (CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING) to define
the padding used for the physical memory mapping section when KASLR
memory is enabled. It ensures there is enough virtual address space when
CONFIG_MEMORY_HOTPLUG is used. The default value is 10 terabytes. If
CONFIG_MEMORY_HOTPLUG is not used, no space is reserved increasing the
entropy available.
Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
arch/x86/Kconfig | 15 +++++++++++++++
arch/x86/mm/kaslr.c | 7 ++++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index adab3fef3bb4..214b3fadbc11 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2010,6 +2010,21 @@ config RANDOMIZE_MEMORY
If unsure, say N.
+config RANDOMIZE_MEMORY_PHYSICAL_PADDING
+ hex "Physical memory mapping padding" if EXPERT
+ depends on RANDOMIZE_MEMORY
+ default "0xa" if MEMORY_HOTPLUG
+ default "0x0"
+ range 0x1 0x40 if MEMORY_HOTPLUG
+ range 0x0 0x40
+ ---help---
+ Define the padding in terabytes added to the existing physical
+ memory size during kernel memory randomization. It is useful
+ for memory hotplug support but reduces the entropy available for
+ address randomization.
+
+ If unsure, leave at the default value.
+
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs"
depends on SMP
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 4f91dc273062..3e9875f7fdda 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -114,8 +114,13 @@ void __init kernel_randomize_memory(void)
if (!kaslr_memory_enabled())
return;
+ /*
+ * Update Physical memory mapping to available and
+ * add padding if needed (especially for memory hotplug support).
+ */
BUG_ON(kaslr_regions[0].base != &page_offset_base);
- memory_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT);
+ memory_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT) +
+ CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
/* Adapt phyiscal memory region size based on available memory */
if (memory_tb < kaslr_regions[0].size_tb)
--
2.7.4
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