From: David Laight <David.Laight@ACULAB.COM>
To: "'Edgecombe, Rick P'" <rick.p.edgecombe@intel.com>,
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Cc: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Subject: RE: [PATCH 18/35] mm: Add guard pages around a shadow stack.
Date: Fri, 11 Feb 2022 09:08:45 +0000 [thread overview]
Message-ID: <09ed01cc5e564ef78875b18001955bb1@AcuMS.aculab.com> (raw)
In-Reply-To: <6a4c11e506874293df13cb94b9dd578bba1819d7.camel@intel.com>
From: Edgecombe, Rick P
> Sent: 10 February 2022 23:43
>
> On Thu, 2022-02-10 at 22:38 +0000, David Laight wrote:
> > Do you need a real guard page?
> > Or is it just enough to ensure that the adjacent page isn't another
> > shadow stack page?
> >
> > Any other page will cause a fault because the PTE isn't
> > readonly+dirty.
> >
> > I'm not sure how common single page allocates are in Linux.
>
> I think it came from this discussion:
>
> https://lore.kernel.org/lkml/CAG48ez1ytOfQyNZMNPFp7XqKcpd7_aRai9G5s7rx0V=8ZG+r2A@mail.gmail.com/#t
>
> > But adjacent shadow stacks may be rare anyway.
> > So a check against both adjacent PTE entries would suffice.
> > Or maybe always allocate an even (or odd) numbered page.
>
> It just needs to not be adjacent to shadow stack memory to do the job.
> Would that be small to implement? It might be a tradeoff of code
> complexity.
That's what I thought.
Although the VA use for guard pages might be a problem in itself.
I'm not sure why I thought shadow stacks would be a single page.
For user space that 'only' allows 512 calls.
For kernel it is a massive waste of memory.
It is probably worth putting multiple kernel shadow stacks into the same page.
(Code that can overrun can do other stuff more easily.)
The hardware engineers failed to think about the implementation (again).
The shadow stack should (probably) run in the opposite direction to
the normal stack.
Then the shadow stack can be placed at the other end of the VA allocated
to a user space stack.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-02-11 9:08 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-30 21:18 [PATCH 00/35] Shadow stacks for userspace Rick Edgecombe
2022-01-30 21:18 ` [PATCH 01/35] Documentation/x86: Add CET description Rick Edgecombe
2022-01-30 21:18 ` [PATCH 02/35] x86/cet/shstk: Add Kconfig option for Shadow Stack Rick Edgecombe
2022-02-07 22:39 ` Dave Hansen
2022-02-08 8:41 ` Thomas Gleixner
2022-02-08 20:20 ` Edgecombe, Rick P
2022-02-08 8:39 ` Thomas Gleixner
2022-01-30 21:18 ` [PATCH 03/35] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Rick Edgecombe
2022-02-07 22:45 ` Dave Hansen
2022-02-08 20:23 ` Edgecombe, Rick P
2022-02-09 1:10 ` Kees Cook
2022-01-30 21:18 ` [PATCH 04/35] x86/cpufeatures: Introduce CPU setup and option parsing for CET Rick Edgecombe
2022-02-07 22:49 ` Dave Hansen
2022-02-08 20:29 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 05/35] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2022-02-07 23:28 ` Dave Hansen
2022-02-08 21:36 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 06/35] x86/cet: Add control-protection fault handler Rick Edgecombe
2022-02-07 23:56 ` Dave Hansen
2022-02-08 22:23 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 07/35] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2022-02-08 0:13 ` Dave Hansen
2022-02-08 22:52 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 08/35] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2022-01-30 21:18 ` [PATCH 09/35] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2022-02-08 1:05 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 10/35] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Rick Edgecombe
2022-02-09 16:58 ` Dave Hansen
2022-02-11 1:39 ` Edgecombe, Rick P
2022-02-11 7:13 ` Wang, Zhi A
2022-02-12 1:45 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 11/35] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2022-02-09 18:00 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 12/35] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2022-02-09 18:30 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 13/35] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2022-01-30 21:18 ` [PATCH 14/35] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2022-02-09 21:55 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 15/35] x86/mm: Check Shadow Stack page fault errors Rick Edgecombe
2022-02-09 19:06 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 16/35] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2022-02-09 21:16 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 17/35] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2022-02-09 21:51 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 18/35] mm: Add guard pages around a shadow stack Rick Edgecombe
2022-02-09 22:23 ` Dave Hansen
2022-02-10 22:38 ` David Laight
2022-02-10 23:42 ` Edgecombe, Rick P
2022-02-11 9:08 ` David Laight [this message]
2022-02-10 22:43 ` Dave Hansen
2022-02-10 23:07 ` Andy Lutomirski
2022-02-10 23:40 ` Edgecombe, Rick P
2022-02-11 17:54 ` Andy Lutomirski
2022-02-12 0:10 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 19/35] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2022-02-09 22:27 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 20/35] mm: Update can_follow_write_pte() for shadow stack Rick Edgecombe
2022-02-09 22:50 ` Dave Hansen
2022-02-09 22:52 ` Dave Hansen
2022-02-10 22:45 ` David Laight
2022-01-30 21:18 ` [PATCH 21/35] mm/mprotect: Exclude shadow stack from preserve_write Rick Edgecombe
2022-02-10 19:27 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 22/35] x86/mm: Prevent VM_WRITE shadow stacks Rick Edgecombe
2022-02-11 22:19 ` Dave Hansen
2022-02-12 1:44 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 23/35] x86/fpu: Add helpers for modifying supervisor xstate Rick Edgecombe
2022-02-08 8:51 ` Thomas Gleixner
2022-02-09 19:55 ` Edgecombe, Rick P
2022-02-12 0:27 ` Dave Hansen
2022-02-12 2:31 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 24/35] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2022-01-30 21:18 ` [PATCH 25/35] x86/cet/shstk: Add user-mode shadow stack support Rick Edgecombe
2022-02-11 23:37 ` Dave Hansen
2022-02-12 0:07 ` Andy Lutomirski
2022-02-12 0:11 ` Dave Hansen
2022-02-12 0:12 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 26/35] x86/process: Change copy_thread() argument 'arg' to 'stack_size' Rick Edgecombe
2022-02-08 8:38 ` Thomas Gleixner
2022-02-11 2:09 ` Edgecombe, Rick P
2022-02-14 12:33 ` Jann Horn
2022-02-15 1:22 ` Edgecombe, Rick P
2022-02-15 8:49 ` Christian Brauner
2022-01-30 21:18 ` [PATCH 27/35] x86/fpu: Add unsafe xsave buffer helpers Rick Edgecombe
2022-01-30 21:18 ` [PATCH 28/35] x86/cet/shstk: Handle thread shadow stack Rick Edgecombe
2022-01-30 21:18 ` [PATCH 29/35] x86/cet/shstk: Introduce shadow stack token setup/verify routines Rick Edgecombe
2022-01-30 21:18 ` [PATCH 30/35] x86/cet/shstk: Handle signals for shadow stack Rick Edgecombe
2022-01-30 21:18 ` [PATCH 31/35] x86/cet/shstk: Add arch_prctl elf feature functions Rick Edgecombe
2022-01-30 21:18 ` [PATCH 32/35] x86/cet/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2022-01-30 21:18 ` [PATCH 33/35] selftests/x86: Add map_shadow_stack syscall test Rick Edgecombe
2022-01-30 21:18 ` Rick Edgecombe
2022-02-03 22:42 ` Dave Hansen
2022-02-04 1:22 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 34/35] x86/cet/shstk: Support wrss for userspace Rick Edgecombe
2022-01-31 7:56 ` Florian Weimer
2022-01-31 18:26 ` H.J. Lu
2022-01-31 18:45 ` Florian Weimer
2022-01-30 21:18 ` [PATCH 35/35] x86/cpufeatures: Limit shadow stack to Intel CPUs Rick Edgecombe
2022-02-03 21:58 ` John Allen
2022-02-03 22:23 ` H.J. Lu
2022-02-04 22:21 ` John Allen
2022-02-03 21:07 ` [PATCH 00/35] Shadow stacks for userspace Thomas Gleixner
2022-02-04 1:08 ` Edgecombe, Rick P
2022-02-04 5:20 ` Andy Lutomirski
2022-02-04 20:23 ` Edgecombe, Rick P
2022-02-05 13:26 ` David Laight
2022-02-05 13:29 ` H.J. Lu
2022-02-05 20:15 ` Edgecombe, Rick P
2022-02-05 20:21 ` H.J. Lu
2022-02-06 13:19 ` Peter Zijlstra
2022-02-06 13:42 ` David Laight
2022-02-06 13:55 ` H.J. Lu
2022-02-07 10:22 ` Florian Weimer
2022-02-08 1:46 ` Edgecombe, Rick P
2022-02-08 1:31 ` Andy Lutomirski
2022-02-08 9:31 ` Thomas Gleixner
2022-02-08 16:15 ` Andy Lutomirski
2022-02-06 13:06 ` Peter Zijlstra
2022-02-06 18:42 ` Mike Rapoport
2022-02-07 7:20 ` Adrian Reber
2022-02-07 16:30 ` Dave Hansen
2022-02-08 9:16 ` Mike Rapoport
2022-02-08 9:29 ` Cyrill Gorcunov
2022-02-08 16:21 ` Andy Lutomirski
2022-02-08 17:02 ` Cyrill Gorcunov
2022-02-08 21:54 ` Dmitry Safonov
2022-02-09 6:37 ` Cyrill Gorcunov
2022-02-09 2:18 ` Edgecombe, Rick P
2022-02-09 6:43 ` Cyrill Gorcunov
2022-02-09 10:53 ` Mike Rapoport
2022-02-10 2:37 ` Andy Lutomirski
2022-02-10 2:53 ` H.J. Lu
2022-02-10 13:52 ` Willgerodt, Felix
2022-02-11 7:41 ` avagin
2022-02-11 8:04 ` Mike Rapoport
2022-02-28 20:27 ` Mike Rapoport
2022-02-28 20:30 ` Andy Lutomirski
2022-02-28 21:30 ` Mike Rapoport
2022-02-28 22:55 ` Andy Lutomirski
2022-03-03 19:40 ` Mike Rapoport
2022-03-03 23:00 ` Andy Lutomirski
2022-03-04 1:30 ` Edgecombe, Rick P
2022-03-04 19:13 ` Andy Lutomirski
2022-03-07 18:56 ` Mike Rapoport
2022-03-07 19:07 ` H.J. Lu
2022-05-31 11:59 ` Mike Rapoport
2022-05-31 16:25 ` Edgecombe, Rick P
2022-05-31 16:36 ` Mike Rapoport
2022-05-31 17:34 ` Edgecombe, Rick P
2022-05-31 18:00 ` H.J. Lu
2022-06-01 17:27 ` Edgecombe, Rick P
2022-06-01 19:27 ` H.J. Lu
2022-06-01 8:06 ` Mike Rapoport
2022-06-01 17:24 ` Edgecombe, Rick P
2022-06-09 18:04 ` Mike Rapoport
2022-03-07 22:21 ` David Laight
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