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From: Kees Cook <kees@kernel.org>
To: David Hildenbrand <david@redhat.com>,
	"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
	"fweimer@redhat.com" <fweimer@redhat.com>
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Subject: Re: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory
Date: Wed, 25 Jan 2023 07:23:27 -0800	[thread overview]
Message-ID: <E857CF98-EEB2-4F83-8305-0A52B463A661@kernel.org> (raw)
In-Reply-To: <716d9e97-b08f-eb0f-101a-be6eaf36f184@redhat.com>

On January 25, 2023 1:29:20 AM PST, David Hildenbrand <david@redhat.com> wrote:
>On 25.01.23 00:41, Edgecombe, Rick P wrote:
>> On Tue, 2023-01-24 at 15:08 -0800, Kees Cook wrote:
>>>> GDB support for shadow stack is queued up for whenever the kernel
>>>> interface settles. I believe it just uses ptrace, and not this
>>>> proc.
>>>> But yea ptrace poke will still need to use FOLL_FORCE and be able
>>>> to
>>>> write through shadow stacks.
>>> 
>>> I'd prefer to avoid adding more FOLL_FORCE if we can. If gdb can do
>>> stack manipulations through a ptrace interface then let's leave off
>>> FOLL_FORCE.
>> 
>> Ptrace and /proc/self/mem both use FOLL_FORCE. I think ptrace will
>> always need it or something like it for debugging.
>> 
>> To jog your memory, this series doesn't change what uses FOLL_FORCE. It
>> just sets the shadow stack rules to be the same as read-only memory. So
>> even though shadow stack memory is sort of writable, it's a bit more
>> locked down and FOLL_FORCE is required to write to it with GUP.
>> 
>> If we just remove FOLL_FORCE from /proc/self/mem, something will
>> probably break right? How do we do this? Some sort of opt-in?
>
>I don't think removing that is an option. It's another debug interface that has been allowing such access for ever ...
>
>Blocking /proc/self/mem access completely for selected processes might be the better alternative.
>

Yeah, this would be nice. Kind of like being undumpable or no_new_privs.



-- 
Kees Cook


  reply	other threads:[~2023-01-25 15:23 UTC|newest]

Thread overview: 120+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-19 21:22 [PATCH v5 00/39] Shadow stacks for userspace Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 01/39] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2023-01-20  0:38   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 02/39] x86/shstk: Add Kconfig option for shadow stack Rick Edgecombe
2023-01-20  0:40   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2023-01-20  0:44   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2023-01-20  0:46   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2023-01-20  0:46   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 06/39] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2023-01-20  0:47   ` Kees Cook
2023-02-01 11:01   ` Borislav Petkov
2023-02-01 17:31     ` Edgecombe, Rick P
2023-02-01 18:18       ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 07/39] x86: Add user control-protection fault handler Rick Edgecombe
2023-01-20  0:50   ` Kees Cook
2023-02-03 19:09   ` Borislav Petkov
2023-02-03 19:24     ` Edgecombe, Rick P
2023-02-03 19:44       ` Borislav Petkov
2023-02-03 23:01         ` Edgecombe, Rick P
2023-02-04 10:37           ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 08/39] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2023-01-20  0:52   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 09/39] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 10/39] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2023-01-20  0:55   ` Kees Cook
2023-01-23  9:16   ` David Hildenbrand
2023-01-23  9:28   ` David Hildenbrand
2023-01-23 20:56     ` Edgecombe, Rick P
2023-01-24 16:28       ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2023-01-20  0:57   ` Kees Cook
2023-02-09 14:08   ` Borislav Petkov
2023-02-09 17:09     ` Edgecombe, Rick P
2023-02-10 13:57       ` Borislav Petkov
2023-02-10 17:00         ` Edgecombe, Rick P
2023-02-17 16:11           ` Borislav Petkov
2023-02-17 16:53             ` Edgecombe, Rick P
2023-01-19 21:22 ` [PATCH v5 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2023-01-20  0:58   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 13/39] x86/mm: Start actually marking _PAGE_COW Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 14/39] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 15/39] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 16/39] x86/mm: Check shadow stack page fault errors Rick Edgecombe
2023-01-20  0:59   ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 17/39] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk Rick Edgecombe
2023-01-23  9:50   ` David Hildenbrand
2023-01-23 20:47     ` Edgecombe, Rick P
2023-01-24 16:24       ` David Hildenbrand
2023-01-24 18:14         ` Edgecombe, Rick P
2023-01-25  9:27           ` David Hildenbrand
2023-01-25 18:43             ` Edgecombe, Rick P
2023-01-26  0:59               ` Edgecombe, Rick P
2023-01-26  8:46                 ` David Hildenbrand
2023-01-26 20:19                   ` Edgecombe, Rick P
2023-01-27 16:12                     ` David Hildenbrand
2023-01-28  0:51                       ` Edgecombe, Rick P
2023-01-31  8:46                         ` David Hildenbrand
2023-01-31 23:33                           ` Edgecombe, Rick P
2023-02-01  9:03                             ` David Hildenbrand
2023-02-01 17:32                               ` Edgecombe, Rick P
2023-02-01 18:03                                 ` David Hildenbrand
2023-01-26  8:57               ` David Hildenbrand
2023-01-26 20:16                 ` Edgecombe, Rick P
2023-01-27 16:19                   ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 19/39] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2023-01-20  1:01   ` Kees Cook
2023-02-14  0:09   ` Deepak Gupta
2023-02-14  1:07     ` Edgecombe, Rick P
2023-02-14  6:10       ` Deepak Gupta
2023-02-14 18:24         ` Edgecombe, Rick P
2023-02-15  6:37           ` Deepak Gupta
2023-01-19 21:22 ` [PATCH v5 20/39] mm: Add guard pages around a shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 21/39] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 22/39] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2023-01-23  9:10   ` David Hildenbrand
2023-01-23 10:45     ` Florian Weimer
2023-01-23 20:46       ` Edgecombe, Rick P
2023-01-24 16:26         ` David Hildenbrand
2023-01-24 18:42           ` Edgecombe, Rick P
2023-01-24 23:08             ` Kees Cook
2023-01-24 23:41               ` Edgecombe, Rick P
2023-01-25  9:29                 ` David Hildenbrand
2023-01-25 15:23                   ` Kees Cook [this message]
2023-01-25 15:36             ` Schimpe, Christina
2023-01-25 16:43               ` Schimpe, Christina
2023-01-19 21:23 ` [PATCH v5 24/39] x86/mm: Introduce MAP_ABOVE4G Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 25/39] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2023-01-20  1:01   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 26/39] x86: Introduce userspace API for shadow stack Rick Edgecombe
2023-01-20  1:04   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 27/39] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2023-01-20  1:05   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 28/39] x86/shstk: Handle thread shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 29/39] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2023-01-20  1:05   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 30/39] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 31/39] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2023-01-20  1:07   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 32/39] x86/shstk: Support WRSS for userspace Rick Edgecombe
2023-01-20  1:06   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 33/39] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 34/39] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 35/39] selftests/x86: Add shadow stack test Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 36/39] x86/fpu: Add helper for initing features Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 37/39] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2023-01-20  1:08   ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 38/39] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 39/39] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
2023-01-20  1:08   ` Kees Cook
2023-01-19 22:26 ` [PATCH v5 00/39] Shadow stacks for userspace Andrew Morton
2023-01-20 17:27   ` Edgecombe, Rick P
2023-01-20 19:19     ` Kees Cook
2023-01-25 19:46       ` Edgecombe, Rick P
2023-01-20 17:48 ` John Allen
2023-01-22  8:20 ` Mike Rapoport

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