Groups > linux.kernel > #1619076

Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap()

From	"PaX Team" <pageexec@freemail.hu>
Newsgroups	linux.kernel
Subject	Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap()
Date	2017-04-07 22:10 +0200
Message-ID	<ttImK-3TM-3@gated-at.bofh.it> (permalink)
References	<ttImK-3TM-5@gated-at.bofh.it> <ttImK-3TM-7@gated-at.bofh.it> <ttEMa-18X-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 7 Apr 2017 at 9:14, Andy Lutomirski wrote:

> On Fri, Apr 7, 2017 at 6:30 AM, Mathias Krause <minipli@googlemail.com> wrote:
> > On 7 April 2017 at 15:14, Thomas Gleixner <tglx@linutronix.de> wrote:
> >> On Fri, 7 Apr 2017, Mathias Krause wrote:
> > Fair enough. However, placing a BUG_ON(!(read_cr0() & X86_CR0_WP))
> > somewhere sensible should make those "leaks" visible fast -- and their
> > exploitation impossible, i.e. fail hard.
> 
> The leaks surely exist and now we'll just add an exploitable BUG.

can you please share those leaks that 'surely exist' and CC oss-security
while at it?

> I think we're approaching this all wrong, actually.  The fact that x86
> has this CR0.WP thing is arguably a historical accident, and the fact
> that PaX uses it doesn't mean that PaX is doing it the best way for
> upstream Linux.
> 
> Why don't we start at the other end and do a generic non-arch-specific
> implementation: set up an mm_struct that contains an RW alias of the
> relevant parts of rodata and use use_mm to access it.  (That is,
> get_fs() to back up the old fs, set_fs(USER_DS),
> use_mm(&rare_write_mm), do the write using copy_to_user, undo
> everything.)
> 
> Then someone who cares about performance can benchmark the CR0.WP
> approach against it and try to argue that it's a good idea.  This
> benchmark should wait until I'm done with my PCID work, because PCID
> is going to make use_mm() a whole heck of a lot faster.

in my measurements switching PCID is hovers around 230 cycles for snb-ivb
and 200-220 for hsw-skl whereas cr0 writes are around 230-240 cycles. there's
of course a whole lot more impact for switching address spaces so it'll never
be fast enough to beat cr0.wp.

Thread

[RFC v2] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 10/11] gcc-plugins: Add constify plugin Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 03/11] net: switch sock_diag handlers to rare_write() Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 07/11] ARM: mm: set DOMAIN_WR_RARE for rodata Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
    Re: [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-29 20:30 +0200
      Re: [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Ho-Eun Ryu <hoeun.ryu@gmail.com> - 2017-03-30 09:50 +0200
        Re: [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-30 19:10 +0200
    Re: [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Ho-Eun Ryu <hoeun.ryu@gmail.com> - 2017-04-07 10:20 +0200
      Re: [RFC v2][PATCH 01/11] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-04-07 22:40 +0200
  [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
    Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@amacapital.net> - 2017-03-30 00:40 +0200
      Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Kees Cook <keescook@chromium.org> - 2017-03-30 03:50 +0200
        Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-06 02:00 +0200
          Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Kees Cook <keescook@chromium.org> - 2017-04-06 02:20 +0200
            Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@amacapital.net> - 2017-04-06 18:00 +0200
              Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Mathias Krause <minipli@googlemail.com> - 2017-04-07 10:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Thomas Gleixner <tglx@linutronix.de> - 2017-04-07 11:50 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Mathias Krause <minipli@googlemail.com> - 2017-04-07 13:00 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Thomas Gleixner <tglx@linutronix.de> - 2017-04-07 15:20 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Mathias Krause <minipli@googlemail.com> - 2017-04-07 15:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-07 18:20 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Mark Rutland <mark.rutland@arm.com> - 2017-04-07 18:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() "PaX Team" <pageexec@freemail.hu> - 2017-04-07 22:10 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-08 07:00 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() "PaX Team" <pageexec@freemail.hu> - 2017-04-09 14:50 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-10 02:20 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() "PaX Team" <pageexec@freemail.hu> - 2017-04-10 12:50 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Thomas Gleixner <tglx@linutronix.de> - 2017-04-07 22:50 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Kees Cook <keescook@chromium.org> - 2017-04-07 23:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Daniel Micay <danielmicay@gmail.com> - 2017-04-08 06:20 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Daniel Micay <danielmicay@gmail.com> - 2017-04-08 06:20 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Daniel Micay <danielmicay@gmail.com> - 2017-04-08 06:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-08 07:10 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Daniel Micay <danielmicay@gmail.com> - 2017-04-08 09:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-08 17:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Ingo Molnar <mingo@kernel.org> - 2017-04-09 13:00 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Mark Rutland <mark.rutland@arm.com> - 2017-04-10 12:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() "PaX Team" <pageexec@freemail.hu> - 2017-04-09 22:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Andy Lutomirski <luto@kernel.org> - 2017-04-10 02:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Thomas Gleixner <tglx@linutronix.de> - 2017-04-07 21:30 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Peter Zijlstra <peterz@infradead.org> - 2017-04-07 16:50 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Mark Rutland <mark.rutland@arm.com> - 2017-04-10 12:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() "PaX Team" <pageexec@freemail.hu> - 2017-04-07 22:40 +0200
                Re: [kernel-hardening] Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Thomas Gleixner <tglx@linutronix.de> - 2017-04-10 10:30 +0200
    Re: [RFC v2][PATCH 04/11] x86: Implement  __arch_rare_write_begin/unmap() Peter Zijlstra <peterz@infradead.org> - 2017-04-07 11:40 +0200
  [RFC v2][PATCH 09/11] list: add rare_write() list helpers Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 05/11] ARM: mm: dump: Add domain to output Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 11/11] cgroups: force all struct cftype const Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
  [RFC v2][PATCH 08/11] ARM: Implement __arch_rare_write_begin/end() Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
    Re: [RFC v2][PATCH 08/11] ARM: Implement  __arch_rare_write_begin/end() Peter Zijlstra <peterz@infradead.org> - 2017-04-07 11:40 +0200
  [RFC v2][PATCH 02/11] lkdtm: add test for rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-29 20:20 +0200
    Re: [kernel-hardening] [RFC v2][PATCH 02/11] lkdtm: add test for  rare_write() infrastructure Ian Campbell <ijc@hellion.org.uk> - 2017-03-30 12:20 +0200
      Re: [kernel-hardening] [RFC v2][PATCH 02/11] lkdtm: add test for  rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-30 18:20 +0200
  Re: [RFC v2] Introduce rare_write() infrastructure Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-03-29 21:10 +0200
    Re: [RFC v2] Introduce rare_write() infrastructure Kees Cook <keescook@chromium.org> - 2017-03-29 21:20 +0200

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