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Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

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On Tue, Jun 21, 2016 at 12:47 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Tue, Jun 21, 2016 at 12:47 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Tuesday, June 21, 2016 10:16:21 AM CEST Kees Cook wrote:
>>> On Tue, Jun 21, 2016 at 2:24 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> > On Monday, June 20, 2016 4:43:30 PM CEST Andy Lutomirski wrote:
>>> >>
>>> >> On my laptop, this adds about 1.5µs of overhead to task creation,
>>> >> which seems to be mainly caused by vmalloc inefficiently allocating
>>> >> individual pages even when a higher-order page is available on the
>>> >> freelist.
>>> >
>>> > Would it help to have a fixed virtual address for the stack instead
>>> > and map the current stack to that during a task switch, similar to
>>> > how we handle fixmap pages?
>>> >
>>> > That would of course trade the allocation overhead for a task switch
>>> > overhead, which may be better or worse. It would also give "current"
>>> > a constant address, which may give a small performance advantage
>>> > but may also introduce a new attack vector unless we randomize it
>>> > again.
>>>
>>> Right: we don't want a fixed address. That makes attacks WAY easier.
>>
>> Do we care about making the address more random then? When I look
>> at /proc/vmallocinfo, I see that allocations are all using
>> consecutive addresses, so if you can figure out the virtual
>> address of the stack for one process that would give you a good
>> chance of guessing the address for the next pid.
>
> Quite possibly.  We should seriously consider at least randomizing the
> *start* of the vmalloc area, at least on 64-bit architectures.

Yup, this is already under way for x86. Thomas Garnier has a series
that he's been working on:

http://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=kaslr/memory

I'd love to see similar for other architectures too.

Thomas just sent me an updated series I'll be putting up for review later today.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security

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[PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 03/13] x86/mm: Remove kernel_unmap_pages_in_pgd() and efi_cleanup_page_tables() Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
    Re: [PATCH v3 03/13] x86/mm: Remove kernel_unmap_pages_in_pgd() and  efi_cleanup_page_tables() Matt Fleming <matt@codeblueprint.co.uk> - 2016-06-21 12:20 +0200
  [PATCH v3 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 06/13] fork: Add generic vmalloced stack support Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
    Re: [PATCH v3 06/13] fork: Add generic vmalloced stack support Jann Horn <jannh@google.com> - 2016-06-21 12:10 +0200
      Re: [PATCH v3 06/13] fork: Add generic vmalloced stack support Andy Lutomirski <luto@amacapital.net> - 2016-06-21 19:10 +0200
        Re: [PATCH v3 06/13] fork: Add generic vmalloced stack support Kees Cook <keescook@chromium.org> - 2016-06-21 19:20 +0200
          Re: [PATCH v3 06/13] fork: Add generic vmalloced stack support Andy Lutomirski <luto@amacapital.net> - 2016-06-21 19:40 +0200
          Re: [kernel-hardening] Re: [PATCH v3 06/13] fork: Add generic  vmalloced stack support Rik van Riel <riel@redhat.com> - 2016-06-21 20:50 +0200
            Re: [kernel-hardening] Re: [PATCH v3 06/13] fork: Add generic  vmalloced stack support Andy Lutomirski <luto@amacapital.net> - 2016-06-21 21:50 +0200
            Re: [kernel-hardening] Re: [PATCH v3 06/13] fork: Add generic vmalloced stack support Arnd Bergmann <arnd@arndb.de> - 2016-06-21 22:00 +0200
  [PATCH v3 04/13] mm: Track NR_KERNEL_STACK in KiB instead of number of stacks Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
    Re: [PATCH v3 04/13] mm: Track NR_KERNEL_STACK in KiB instead of  number of stacks Michal Hocko <mhocko@kernel.org> - 2016-06-22 10:50 +0200
  [PATCH v3 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  [PATCH v3 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski <luto@kernel.org> - 2016-06-21 01:50 +0200
  Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-21 06:10 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-21 18:50 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-21 19:20 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-21 19:40 +0200
          Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Kees Cook <keescook@chromium.org> - 2016-06-21 20:20 +0200
            Re: [kernel-hardening] Re: [PATCH v3 00/13] Virtually mapped stacks  with guard pages (x86, core) Rik van Riel <riel@redhat.com> - 2016-06-21 20:30 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-23 03:30 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 08:10 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Oleg Nesterov <oleg@redhat.com> - 2016-06-23 16:40 +0200
          Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 18:40 +0200
            Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-23 18:50 +0200
              Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Oleg Nesterov <oleg@redhat.com> - 2016-06-23 19:20 +0200
            Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Oleg Nesterov <oleg@redhat.com> - 2016-06-23 19:10 +0200
  Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Arnd Bergmann <arnd@arndb.de> - 2016-06-21 11:40 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Kees Cook <keescook@chromium.org> - 2016-06-21 19:30 +0200
      Re: [kernel-hardening] Re: [PATCH v3 00/13] Virtually mapped stacks  with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-21 20:10 +0200
      Re: [kernel-hardening] Re: [PATCH v3 00/13] Virtually mapped stacks  with guard pages (x86, core) Rik van Riel <riel@redhat.com> - 2016-06-21 20:10 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-21 21:50 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Kees Cook <keescook@chromium.org> - 2016-06-21 22:20 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Arnd Bergmann <arnd@arndb.de> - 2016-06-21 21:50 +0200

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