[PATCH v18 00/25] Control-flow Enforcement: Shadow Stack

Yu-cheng Yu
2021-01-27T21:32:20Z

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 [3], and
- Selftests [4].

I have run tests on these patches for quite some time, and they have been
very stable. 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. I will be working to address any
issues should they come up.

Changes in v18:
- Patch #2: change X86_CET_USER to X86_CET
- Patch #4: move setting of X86_FEATURE_CET from get_cpu_cap() to
bsp_init_intel().
- Patch #6: change printk_ratelimit() to __ratelimit(), pr_info() to
pr_emerg(), and do panic() for kernel-mode control protection fault.
- patch #8: make p*_wrprotect() more readable by using p*_set_flags()/
p*_clear_flags() directly.
- patch #11: move reading old_pte out of while() loop. Update comments.
- patch #22: merge GNU_PROPERTY_* definitions and arch_setup_elf_property()
into one patch.
- Rebase to v5.11-rc5

[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] CET Shadow Stack patches v17:

https://lkml.kernel.org/r/20201229213053.16395-1-yu-cheng.yu@intel.com/

[3] Indirect Branch Tracking patches v17.

https://lkml.kernel.org/r/20201229213350.17010-1-yu-cheng.yu@intel.com/

[4] 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/

[5] 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 (25):
Documentation/x86: Add CET description
x86/cet/shstk: Add Kconfig option for user-mode control-flow
protection
x86/cpufeatures: Add CET CPU feature flags for Control-flow
Enforcement Technology (CET)
x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions
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: 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: Introduce VM_SHSTK 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: Re-introduce vm_flags to do_mmap()
x86/cet/shstk: User-mode shadow stack support
x86/cet/shstk: Handle signals for shadow stack
ELF: Introduce arch_setup_elf_property()
x86/cet/shstk: Handle thread shadow stack
x86/cet/shstk: Add arch_prctl functions for shadow stack
mm: Introduce PROT_SHSTK for shadow stack

.../admin-guide/kernel-parameters.txt | 6 +
Documentation/x86/index.rst | 1 +
Documentation/x86/intel_cet.rst | 136 +++++++
arch/arm64/include/asm/elf.h | 5 +
arch/x86/Kconfig | 28 ++
arch/x86/Kconfig.assembler | 5 +
arch/x86/ia32/ia32_signal.c | 17 +
arch/x86/include/asm/cet.h | 42 +++
arch/x86/include/asm/cpufeatures.h | 4 +-
arch/x86/include/asm/disabled-features.h | 17 +-
arch/x86/include/asm/elf.h | 13 +
arch/x86/include/asm/fpu/internal.h | 10 +
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 | 85 +++++
arch/x86/include/asm/mmu_context.h | 3 +
arch/x86/include/asm/msr-index.h | 19 +
arch/x86/include/asm/page_64_types.h | 10 +
arch/x86/include/asm/pgtable.h | 194 +++++++++-
arch/x86/include/asm/pgtable_types.h | 48 ++-
arch/x86/include/asm/processor.h | 5 +
arch/x86/include/asm/special_insns.h | 32 ++
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/include/uapi/asm/sigcontext.h | 9 +
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/cet.c | 343 ++++++++++++++++++
arch/x86/kernel/cet_prctl.c | 68 ++++
arch/x86/kernel/cpu/common.c | 16 +
arch/x86/kernel/cpu/cpuid-deps.c | 2 +
arch/x86/kernel/cpu/intel.c | 3 +
arch/x86/kernel/fpu/signal.c | 100 +++++
arch/x86/kernel/fpu/xstate.c | 10 +-
arch/x86/kernel/idt.c | 4 +
arch/x86/kernel/process.c | 14 +-
arch/x86/kernel/process_64.c | 32 ++
arch/x86/kernel/signal.c | 10 +
arch/x86/kernel/signal_compat.c | 2 +-
arch/x86/kernel/traps.c | 60 +++
arch/x86/mm/fault.c | 19 +
arch/x86/mm/mmap.c | 2 +
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 | 38 +-
include/linux/pgtable.h | 35 ++
include/uapi/asm-generic/siginfo.h | 3 +-
include/uapi/linux/elf.h | 9 +
ipc/shm.c | 2 +-
mm/gup.c | 8 +-
mm/huge_memory.c | 10 +-
mm/memory.c | 5 +-
mm/migrate.c | 3 +-
mm/mmap.c | 23 +-
mm/mprotect.c | 2 +-
mm/nommu.c | 4 +-
mm/util.c | 2 +-
64 files changed, 1549 insertions(+), 84 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.c
create mode 100644 arch/x86/kernel/cet_prctl.c

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2.21.0