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* [PATCH v7 0/9] x86/mm: memory area address KASLR
@ 2016-06-22  0:46 ` Kees Cook
  0 siblings, 0 replies; 74+ messages in thread
From: Kees Cook @ 2016-06-22  0:46 UTC (permalink / raw)
  To: Ingo Molnar
  Cc: Kees Cook, Thomas Garnier, Andy Lutomirski, x86, Borislav Petkov,
	Baoquan He, Yinghai Lu, Juergen Gross, Matt Fleming, Toshi Kani,
	Andrew Morton, Dan Williams, Kirill A. Shutemov, Dave Hansen,
	Xiao Guangrong, Martin Schwidefsky, Aneesh Kumar K.V,
	Alexander Kuleshov, Alexander Popov, Dave Young, Joerg Roedel,
	Lv Zheng, Mark Salter, Dmitry Vyukov, Stephen Smalley,
	Boris Ostrovsky, Christian Borntraeger, Jan Beulich,
	linux-kernel, Jonathan Corbet, linux-doc, kernel-hardening

This is v7 of Thomas Garnier's KASLR for memory areas (physical memory
mapping, vmalloc, vmemmap). It expects to be applied on top of the
x86/boot tip.

The current implementation of KASLR randomizes only the base address of
the kernel and its modules. Research was published showing that static
memory addresses can be found and used in exploits, effectively ignoring
base address KASLR:

   The physical memory mapping holds most allocations from boot and
   heap allocators. Knowning the base address and physical memory
   size, an attacker can deduce the PDE virtual address for the vDSO
   memory page.  This attack was demonstrated at CanSecWest 2016, in
   the "Getting Physical: Extreme Abuse of Intel Based Paged Systems"
   https://goo.gl/ANpWdV (see second part of the presentation). The
   exploits used against Linux worked successfuly against 4.6+ but fail
   with KASLR memory enabled (https://goo.gl/iTtXMJ). Similar research
   was done at Google leading to this patch proposal. Variants exists
   to overwrite /proc or /sys objects ACLs leading to elevation of
   privileges.  These variants were tested against 4.6+.

This set of patches randomizes the base address and padding of three
major memory sections (physical memory mapping, vmalloc, and vmemmap).
It mitigates exploits relying on predictable kernel addresses in these
areas. This feature can be enabled with the CONFIG_RANDOMIZE_MEMORY
option. (This CONFIG, along with CONFIG_RANDOMIZE may be renamed in
the future, but stands for now as other architectures continue to
implement KASLR.)

Padding for the memory hotplug support is managed by
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING. The default value is 10
terabytes.

The patches were tested on qemu & physical machines. Xen compatibility was
also verified. Multiple reboots were used to verify entropy for each
memory section.

Notable problems that needed solving:
 - The three target memory sections need to not be at the same place
   across reboots.
 - The physical memory mapping can use a virtual address not aligned on
   the PGD page table.
 - Reasonable entropy is needed early at boot before get_random_bytes()
   is available.
 - Memory hotplug needs KASLR padding.

Patches:
 - 1: refactor KASLR functions (moves them from boot/compressed/ into lib/)
 - 2: clarifies the variables used for physical mapping.
 - 3: PUD virtual address support for physical mapping.
 - 4: split out the trampoline PGD
 - 5: KASLR memory infrastructure code
 - 6: randomize base of physical mapping region
 - 7: randomize base of vmalloc region
 - 8: randomize base of vmemmap region
 - 9: provide memory hotplug padding support

There is no measurable performance impact:

 - Kernbench shows almost no difference (-+ less than 1%).
 - Hackbench shows 0% difference on average (hackbench 90 repeated 10 times).

^ permalink raw reply	[flat|nested] 74+ messages in thread

end of thread, other threads:[~2016-08-18 10:51 UTC | newest]

Thread overview: 74+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-06-22  0:46 [PATCH v7 0/9] x86/mm: memory area address KASLR Kees Cook
2016-06-22  0:46 ` [kernel-hardening] " Kees Cook
2016-06-22  0:46 ` [PATCH v7 1/9] x86/mm: Refactor KASLR entropy functions Kees Cook
2016-06-22  0:46   ` [kernel-hardening] " Kees Cook
2016-07-08 20:33   ` [tip:x86/boot] " tip-bot for Thomas Garnier
2016-06-22  0:46 ` [PATCH v7 2/9] x86/mm: Update physical mapping variable names (x86_64) Kees Cook
2016-06-22  0:46   ` [kernel-hardening] " Kees Cook
2016-07-08 20:34   ` [tip:x86/boot] x86/mm: Update physical mapping variable names tip-bot for Thomas Garnier
2016-06-22  0:47 ` [PATCH v7 3/9] x86/mm: PUD VA support for physical mapping (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:34   ` [tip:x86/boot] x86/mm: Add PUD VA support for physical mapping tip-bot for Thomas Garnier
2016-06-22  0:47 ` [PATCH v7 4/9] x86/mm: Separate variable for trampoline PGD (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:35   ` [tip:x86/boot] x86/mm: Separate variable for trampoline PGD tip-bot for Thomas Garnier
2016-06-22  0:47 ` [PATCH v7 5/9] x86/mm: Implement ASLR for kernel memory regions (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:35   ` [tip:x86/boot] x86/mm: Implement ASLR for kernel memory regions tip-bot for Thomas Garnier
2016-06-22  0:47 ` [PATCH v7 6/9] x86/mm: Enable KASLR for physical mapping memory region (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:35   ` [tip:x86/boot] x86/mm: Enable KASLR for physical mapping memory regions tip-bot for Thomas Garnier
2016-08-14  4:25     ` Brian Gerst
2016-08-14 23:26       ` Baoquan He
2016-08-16 11:31         ` Brian Gerst
2016-08-16 13:42           ` Borislav Petkov
2016-08-16 13:49             ` Borislav Petkov
2016-08-16 15:54               ` Borislav Petkov
2016-08-16 17:50                 ` Borislav Petkov
2016-08-16 19:49                   ` Kees Cook
2016-08-16 21:01                     ` Borislav Petkov
2016-08-17  0:31                       ` Brian Gerst
2016-08-17  9:11                         ` Borislav Petkov
2016-08-17 10:19                           ` Ingo Molnar
2016-08-17 11:33                             ` Borislav Petkov
2016-08-18 10:49                               ` [tip:x86/urgent] x86/microcode/AMD: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y tip-bot for Borislav Petkov
2016-06-22  0:47 ` [PATCH v7 7/9] x86/mm: Enable KASLR for vmalloc memory region (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:36   ` [tip:x86/boot] x86/mm: Enable KASLR for vmalloc memory regions tip-bot for Thomas Garnier
2016-06-22  0:47 ` [PATCH v7 8/9] x86/mm: Enable KASLR for vmemmap memory region (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-06-22  0:47 ` [PATCH v7 9/9] x86/mm: Memory hotplug support for KASLR memory randomization (x86_64) Kees Cook
2016-06-22  0:47   ` [kernel-hardening] " Kees Cook
2016-07-08 20:36   ` [tip:x86/boot] x86/mm: Add memory hotplug support for KASLR memory randomization tip-bot for Thomas Garnier
2016-06-22 12:47 ` [kernel-hardening] [PATCH v7 0/9] x86/mm: memory area address KASLR Jason Cooper
2016-06-22 15:59   ` Thomas Garnier
2016-06-22 17:05     ` Kees Cook
2016-06-22 17:05       ` Kees Cook
2016-06-23 19:33       ` Jason Cooper
2016-06-23 19:33         ` Jason Cooper
2016-06-23 19:45         ` Sandy Harris
2016-06-23 19:59           ` Kees Cook
2016-06-23 19:59             ` Kees Cook
2016-06-23 20:19             ` Jason Cooper
2016-06-23 20:16           ` Jason Cooper
2016-06-23 19:58         ` Kees Cook
2016-06-23 19:58           ` Kees Cook
2016-06-23 20:05           ` Ard Biesheuvel
2016-06-23 20:05             ` Ard Biesheuvel
2016-06-24  1:11             ` Jason Cooper
2016-06-24  1:11               ` Jason Cooper
2016-06-24 10:54               ` Ard Biesheuvel
2016-06-24 10:54                 ` Ard Biesheuvel
2016-06-24 16:02                 ` devicetree random-seed properties, was: "Re: [PATCH v7 0/9] x86/mm: memory area address KASLR" Jason Cooper
2016-06-24 16:02                   ` [kernel-hardening] " Jason Cooper
2016-06-24 19:04                   ` Kees Cook
2016-06-24 19:04                     ` [kernel-hardening] " Kees Cook
2016-06-24 20:40                     ` Andy Lutomirski
2016-06-24 20:40                       ` [kernel-hardening] " Andy Lutomirski
2016-06-30 21:48                       ` Jason Cooper
2016-06-30 21:48                         ` [kernel-hardening] " Jason Cooper
2016-06-30 21:56                         ` Thomas Garnier
2016-06-30 21:48                     ` Jason Cooper
2016-06-30 21:48                       ` [kernel-hardening] " Jason Cooper
2016-07-07 22:24 ` [PATCH v7 0/9] x86/mm: memory area address KASLR Kees Cook
2016-07-07 22:24   ` [kernel-hardening] " Kees Cook

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