mbox series

[v28,00/32] Control-flow Enforcement: Shadow Stack

Message ID 20210722205219.7934-1-yu-cheng.yu@intel.com (mailing list archive)
Headers show
Series Control-flow Enforcement: Shadow Stack | expand

Message

Yu-cheng Yu July 22, 2021, 8:51 p.m. UTC 
Control-flow Enforcement (CET) is a new Intel processor feature that blocks
return/jump-oriented programming attacks.  Details are in "Intel 64 and
IA-32 Architectures Software Developer's Manual" [1].

CET can protect applications and the kernel.  This series enables only
application-level protection, and has three parts:

  - Shadow stack [2],
  - Indirect branch tracking, and
  - Selftests [3].

Linux distributions with CET are available now, and Intel processors with CET
are already on the market.  It would be nice if CET support can be accepted
into the kernel.

Changes in v28:
- Rebase to Linus tree v5.14-rc2.
- Patch #1: Update Document to indicate no-user-shstk also disables IBT.
- Patch #23: Update shstk_setup() with wrmsrl_safe().  Update return value.
- Patch #25: Split out copy_thread() changes.  Add support for old clone().
  Add comments.
- Add comments for get_xsave_addr() (Patch #25, #26).

Changes in v27:
- Eliminate signal context extension structure.  Simplify signal handling.
- Add a new patch to move VM_UFFD_MINOR_BIT to 38.
- Smaller changes are in each patch's log.
- Rebase to Linus tree v5.13-rc2.

[1] Intel 64 and IA-32 Architectures Software Developer's Manual:

    https://software.intel.com/en-us/download/intel-64-and-ia-32-
    architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4

[2] Shadow Stack patches v27:

    https://lore.kernel.org/r/20210521221211.29077-1-yu-cheng.yu@intel.com/

[3] I am holding off the selftests changes and working to get Reviewed-by's.
    The earlier version of the selftests patches:

    https://lkml.kernel.org/r/20200521211720.20236-1-yu-cheng.yu@intel.com/

[4] The kernel ptrace patch is tested with an Intel-internal updated GDB.
    I am holding off the kernel ptrace patch to re-test it with my earlier
    patch for fixing regset holes.

Yu-cheng Yu (32):
  Documentation/x86: Add CET description
  x86/cet/shstk: Add Kconfig option for Shadow Stack
  x86/cpufeatures: Add CET CPU feature flags for Control-flow
    Enforcement Technology (CET)
  x86/cpufeatures: Introduce CPU setup and option parsing for CET
  x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states
  x86/cet: Add control-protection fault handler
  x86/mm: Remove _PAGE_DIRTY from kernel RO pages
  x86/mm: Move pmd_write(), pud_write() up in the file
  x86/mm: Introduce _PAGE_COW
  drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS
  x86/mm: Update pte_modify for _PAGE_COW
  x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for
    transition from _PAGE_DIRTY to _PAGE_COW
  mm: Move VM_UFFD_MINOR_BIT from 37 to 38
  mm: Introduce VM_SHADOW_STACK for shadow stack memory
  x86/mm: Shadow Stack page fault error checking
  x86/mm: Update maybe_mkwrite() for shadow stack
  mm: Fixup places that call pte_mkwrite() directly
  mm: Add guard pages around a shadow stack.
  mm/mmap: Add shadow stack pages to memory accounting
  mm: Update can_follow_write_pte() for shadow stack
  mm/mprotect: Exclude shadow stack from preserve_write
  mm: Re-introduce vm_flags to do_mmap()
  x86/cet/shstk: Add user-mode shadow stack support
  x86/process: Change copy_thread() argument 'arg' to 'stack_size'
  x86/cet/shstk: Handle thread shadow stack
  x86/cet/shstk: Introduce shadow stack token setup/verify routines
  x86/cet/shstk: Handle signals for shadow stack
  ELF: Introduce arch_setup_elf_property()
  x86/cet/shstk: Add arch_prctl functions for shadow stack
  mm: Move arch_calc_vm_prot_bits() to arch/x86/include/asm/mman.h
  mm: Update arch_validate_flags() to test vma anonymous
  mm: Introduce PROT_SHADOW_STACK for shadow stack

 .../admin-guide/kernel-parameters.txt         |   7 +
 Documentation/filesystems/proc.rst            |   1 +
 Documentation/x86/index.rst                   |   1 +
 Documentation/x86/intel_cet.rst               | 139 +++++++
 arch/arm64/include/asm/elf.h                  |   5 +
 arch/arm64/include/asm/mman.h                 |   4 +-
 arch/sparc/include/asm/mman.h                 |   4 +-
 arch/x86/Kconfig                              |  24 ++
 arch/x86/Kconfig.assembler                    |   5 +
 arch/x86/ia32/ia32_signal.c                   |  25 +-
 arch/x86/include/asm/cet.h                    |  53 +++
 arch/x86/include/asm/cpufeatures.h            |   2 +
 arch/x86/include/asm/disabled-features.h      |   8 +-
 arch/x86/include/asm/elf.h                    |  11 +
 arch/x86/include/asm/fpu/types.h              |  23 +-
 arch/x86/include/asm/fpu/xstate.h             |   6 +-
 arch/x86/include/asm/idtentry.h               |   4 +
 arch/x86/include/asm/mman.h                   |  88 ++++
 arch/x86/include/asm/mmu_context.h            |   3 +
 arch/x86/include/asm/msr-index.h              |  19 +
 arch/x86/include/asm/page_types.h             |   7 +
 arch/x86/include/asm/pgtable.h                | 300 ++++++++++++--
 arch/x86/include/asm/pgtable_types.h          |  48 ++-
 arch/x86/include/asm/processor.h              |   5 +
 arch/x86/include/asm/special_insns.h          |  30 ++
 arch/x86/include/asm/trap_pf.h                |   2 +
 arch/x86/include/uapi/asm/mman.h              |  28 +-
 arch/x86/include/uapi/asm/prctl.h             |   4 +
 arch/x86/include/uapi/asm/processor-flags.h   |   2 +
 arch/x86/kernel/Makefile                      |   2 +
 arch/x86/kernel/cet_prctl.c                   |  60 +++
 arch/x86/kernel/cpu/common.c                  |  14 +
 arch/x86/kernel/cpu/cpuid-deps.c              |   2 +
 arch/x86/kernel/fpu/xstate.c                  |  11 +-
 arch/x86/kernel/idt.c                         |   4 +
 arch/x86/kernel/process.c                     |  21 +-
 arch/x86/kernel/process_64.c                  |  27 ++
 arch/x86/kernel/shstk.c                       | 375 ++++++++++++++++++
 arch/x86/kernel/signal.c                      |  13 +
 arch/x86/kernel/signal_compat.c               |   2 +-
 arch/x86/kernel/traps.c                       |  63 +++
 arch/x86/mm/fault.c                           |  19 +
 arch/x86/mm/mmap.c                            |  48 +++
 arch/x86/mm/pat/set_memory.c                  |   2 +-
 arch/x86/mm/pgtable.c                         |  25 ++
 drivers/gpu/drm/i915/gvt/gtt.c                |   2 +-
 fs/aio.c                                      |   2 +-
 fs/binfmt_elf.c                               |   4 +
 fs/proc/task_mmu.c                            |   3 +
 include/linux/elf.h                           |   6 +
 include/linux/mm.h                            |  20 +-
 include/linux/mman.h                          |   2 +-
 include/linux/pgtable.h                       |   7 +
 include/uapi/asm-generic/siginfo.h            |   3 +-
 include/uapi/linux/elf.h                      |  14 +
 ipc/shm.c                                     |   2 +-
 mm/gup.c                                      |  16 +-
 mm/huge_memory.c                              |  27 +-
 mm/memory.c                                   |   5 +-
 mm/migrate.c                                  |   3 +-
 mm/mmap.c                                     |  17 +-
 mm/mprotect.c                                 |  11 +-
 mm/nommu.c                                    |   4 +-
 mm/util.c                                     |   2 +-
 64 files changed, 1581 insertions(+), 115 deletions(-)
 create mode 100644 Documentation/x86/intel_cet.rst
 create mode 100644 arch/x86/include/asm/cet.h
 create mode 100644 arch/x86/include/asm/mman.h
 create mode 100644 arch/x86/kernel/cet_prctl.c
 create mode 100644 arch/x86/kernel/shstk.c

Comments

Dave Hansen July 22, 2021, 9:08 p.m. UTC | #1 
On 7/22/21 1:51 PM, Yu-cheng Yu wrote:
> Linux distributions with CET are available now, and Intel processors with CET
> are already on the market.  It would be nice if CET support can be accepted
> into the kernel.
> 
> Changes in v28:
> - Rebase to Linus tree v5.14-rc2.
> - Patch #1: Update Document to indicate no-user-shstk also disables IBT.
> - Patch #23: Update shstk_setup() with wrmsrl_safe().  Update return value.
> - Patch #25: Split out copy_thread() changes.  Add support for old clone().
>   Add comments.
> - Add comments for get_xsave_addr() (Patch #25, #26).

Could you characterize where this whole thing is?

Are we at the point where the feedback is slowing down?  What kind of
feedback are you getting?  How stable is the ABI versus the last revision?
Yu-cheng Yu July 23, 2021, 5:28 p.m. UTC | #2 
On 7/22/2021 2:08 PM, Dave Hansen wrote:
> On 7/22/21 1:51 PM, Yu-cheng Yu wrote:
>> Linux distributions with CET are available now, and Intel processors with CET
>> are already on the market.  It would be nice if CET support can be accepted
>> into the kernel.
>>
>> Changes in v28:
>> - Rebase to Linus tree v5.14-rc2.
>> - Patch #1: Update Document to indicate no-user-shstk also disables IBT.
>> - Patch #23: Update shstk_setup() with wrmsrl_safe().  Update return value.
>> - Patch #25: Split out copy_thread() changes.  Add support for old clone().
>>    Add comments.
>> - Add comments for get_xsave_addr() (Patch #25, #26).
> 
> Could you characterize where this whole thing is?
> 
> Are we at the point where the feedback is slowing down?  What kind of
> feedback are you getting?  How stable is the ABI versus the last revision?
> 

The ABI has not changed since last version, except the addition of 
shadow stack support for legacy clone().  This does not de-stabilize the 
ABI.

Looking back at recent feedback:

- Boris had given lots of comments on code flow, syntax, etc.  Those are 
all addressed.

- Andy L. commented on the signal handling part, especially the 
introduction of a ucontext extension.  That is eliminated and now there 
is the UC_WAIT_ENDBR flag.

- Kirill commented a few issues on mm patches.  Those are addressed.

- Peter Z. requested splitting shadow stack and ibt.  That is done.

As for running/testing of the series, overall it is stable.

Yu-cheng