Hi, This series implements Shadow Stacks for userspace using x86's Control-flow Enforcement Technology (CET). CET consists of two related security features: shadow stacks and indirect branch tracking. This series implements just the shadow stack part of this feature, and just for userspace. The main use case for shadow stack is providing protection against return oriented programming attacks. It works by maintaining a secondary (shadow) stack using a special memory type that has protections against modification. When executing a CALL instruction, the processor pushes the return address to both the normal stack and to the special permission shadow stack. Upon RET, the processor pops the shadow stack copy and compares it to the normal stack copy. For more details, see the coverletter from v1 [0]. The comments on the last version were mainly code style and verbiage. There was also some late but great questions on the overall design, raised by people starting to look at implementing non-x86 shadow stack features. After discussion on the history and purpose of the design choices, the changes that ultimately came out of the discussion were documentation updates. Some of the concerns were eventually found to be based on misunderstandings of the x86 shadow stack HW limitations. Others were taken as future enhancements. There was a fair amount of discussion on adding the map_shadow_stack syscall instead of building new behaviors into mmap(). Ultimately, since there was no consensus and it was agreed that there wasn't impact on other archs, this was left as well. Lastly, per Dave, the author for most of the the patches from the old series has been swapped to me from Yu-cheng, so potential bisecters can find help better. Previously these patches had me just as Co-developed-by. At this point, I think we have a pretty good initial shadow stack implementation here. I'd like to start with the basics and let real world usage inform the enhancements if we can. Unless anyone sees any likely ABI trap we are walking into. I left tags in place. Previous version [1]. Thanks, Rick [0] https://lore.kernel.org/lkml/20220130211838.8382-1-rick.p.edgecombe@xxxxxxxxx/ [1] https://lore.kernel.org/lkml/20230227222957.24501-1-rick.p.edgecombe@xxxxxxxxx/ Mike Rapoport (1): x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe (36): Documentation/x86: Add CET shadow stack description x86/shstk: Add Kconfig option for shadow stack x86/cpufeatures: Add CPU feature flags for shadow stacks x86/cpufeatures: Enable CET CR4 bit for shadow stack x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states x86/fpu: Add helper for modifying xstate x86/traps: Move control protection handler to separate file x86/shstk: Add user control-protection fault handler x86/mm: Remove _PAGE_DIRTY from kernel RO pages x86/mm: Move pmd_write(), pud_write() up in the file mm: Introduce pte_mkwrite_kernel() s390/mm: Introduce pmd_mkwrite_kernel() mm: Make pte_mkwrite() take a VMA x86/mm: Introduce _PAGE_SAVED_DIRTY x86/mm: Update ptep/pmdp_set_wrprotect() for _PAGE_SAVED_DIRTY x86/mm: Start actually marking _PAGE_SAVED_DIRTY x86/mm: Check shadow stack page fault errors x86/mm: Teach pte_mkwrite() about stack memory mm: Add guard pages around a shadow stack. mm/mmap: Add shadow stack pages to memory accounting mm: Don't allow write GUPs to shadow stack memory x86/mm: Introduce MAP_ABOVE4G mm: Warn on shadow stack memory in wrong vma x86/mm: Warn if create Write=0,Dirty=1 with raw prot x86: Introduce userspace API for shadow stack x86/shstk: Add user-mode shadow stack support x86/shstk: Handle thread shadow stack x86/shstk: Introduce routines modifying shstk x86/shstk: Handle signals for shadow stack x86/shstk: Introduce map_shadow_stack syscall x86/shstk: Support WRSS for userspace x86: Expose thread features in /proc/$PID/status x86/shstk: Wire in shadow stack interface selftests/x86: Add shadow stack test x86: Add PTRACE interface for shadow stack x86/shstk: Add ARCH_SHSTK_STATUS Yu-cheng Yu (3): mm: Move VM_UFFD_MINOR_BIT from 37 to 38 mm: Introduce VM_SHADOW_STACK for shadow stack memory mm: Re-introduce vm_flags to do_mmap() Documentation/filesystems/proc.rst | 1 + Documentation/mm/arch_pgtable_helpers.rst | 9 +- Documentation/x86/index.rst | 1 + Documentation/x86/shstk.rst | 179 +++++ arch/alpha/include/asm/pgtable.h | 6 +- arch/arc/include/asm/hugepage.h | 2 +- arch/arc/include/asm/pgtable-bits-arcv2.h | 7 +- arch/arm/include/asm/pgtable-3level.h | 7 +- arch/arm/include/asm/pgtable.h | 2 +- arch/arm/kernel/signal.c | 2 +- arch/arm64/include/asm/pgtable.h | 9 +- arch/arm64/kernel/signal.c | 2 +- arch/arm64/kernel/signal32.c | 2 +- arch/arm64/mm/trans_pgd.c | 4 +- arch/csky/include/asm/pgtable.h | 2 +- arch/hexagon/include/asm/pgtable.h | 2 +- arch/ia64/include/asm/pgtable.h | 2 +- arch/loongarch/include/asm/pgtable.h | 4 +- arch/m68k/include/asm/mcf_pgtable.h | 2 +- arch/m68k/include/asm/motorola_pgtable.h | 6 +- arch/m68k/include/asm/sun3_pgtable.h | 6 +- arch/microblaze/include/asm/pgtable.h | 2 +- arch/mips/include/asm/pgtable.h | 6 +- arch/nios2/include/asm/pgtable.h | 2 +- arch/openrisc/include/asm/pgtable.h | 2 +- arch/parisc/include/asm/pgtable.h | 6 +- arch/powerpc/include/asm/book3s/32/pgtable.h | 2 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +- arch/powerpc/include/asm/nohash/32/pgtable.h | 2 +- arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +- arch/powerpc/include/asm/nohash/64/pgtable.h | 2 +- arch/riscv/include/asm/pgtable.h | 6 +- arch/s390/include/asm/hugetlb.h | 4 +- arch/s390/include/asm/pgtable.h | 14 +- arch/s390/mm/pageattr.c | 4 +- arch/sh/include/asm/pgtable_32.h | 10 +- arch/sparc/include/asm/pgtable_32.h | 2 +- arch/sparc/include/asm/pgtable_64.h | 6 +- arch/sparc/kernel/signal32.c | 2 +- arch/sparc/kernel/signal_64.c | 2 +- arch/um/include/asm/pgtable.h | 2 +- arch/x86/Kconfig | 24 + arch/x86/Kconfig.assembler | 5 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/x86/include/asm/cpufeatures.h | 2 + arch/x86/include/asm/disabled-features.h | 16 +- arch/x86/include/asm/fpu/api.h | 9 + arch/x86/include/asm/fpu/regset.h | 7 +- arch/x86/include/asm/fpu/sched.h | 3 +- arch/x86/include/asm/fpu/types.h | 16 +- arch/x86/include/asm/fpu/xstate.h | 6 +- arch/x86/include/asm/idtentry.h | 2 +- arch/x86/include/asm/mmu_context.h | 2 + arch/x86/include/asm/pgtable.h | 322 +++++++- arch/x86/include/asm/pgtable_types.h | 56 +- arch/x86/include/asm/processor.h | 8 + arch/x86/include/asm/shstk.h | 38 + arch/x86/include/asm/special_insns.h | 13 + arch/x86/include/asm/tlbflush.h | 3 +- arch/x86/include/asm/trap_pf.h | 2 + arch/x86/include/asm/traps.h | 12 + arch/x86/include/uapi/asm/mman.h | 4 + arch/x86/include/uapi/asm/prctl.h | 12 + arch/x86/kernel/Makefile | 4 + arch/x86/kernel/cet.c | 152 ++++ arch/x86/kernel/cpu/common.c | 35 +- arch/x86/kernel/cpu/cpuid-deps.c | 1 + arch/x86/kernel/cpu/proc.c | 23 + arch/x86/kernel/fpu/core.c | 54 +- arch/x86/kernel/fpu/regset.c | 78 ++ arch/x86/kernel/fpu/xstate.c | 90 ++- arch/x86/kernel/idt.c | 2 +- arch/x86/kernel/process.c | 21 +- arch/x86/kernel/process_64.c | 9 +- arch/x86/kernel/ptrace.c | 12 + arch/x86/kernel/shstk.c | 499 +++++++++++++ arch/x86/kernel/signal.c | 1 + arch/x86/kernel/signal_32.c | 2 +- arch/x86/kernel/signal_64.c | 8 +- arch/x86/kernel/sys_x86_64.c | 6 +- arch/x86/kernel/traps.c | 87 --- arch/x86/mm/fault.c | 22 + arch/x86/mm/pat/set_memory.c | 4 +- arch/x86/mm/pgtable.c | 38 + arch/x86/xen/enlighten_pv.c | 2 +- arch/x86/xen/mmu_pv.c | 2 +- arch/x86/xen/xen-asm.S | 2 +- arch/xtensa/include/asm/pgtable.h | 2 +- fs/aio.c | 2 +- fs/proc/array.c | 6 + fs/proc/task_mmu.c | 3 + include/asm-generic/hugetlb.h | 4 +- include/linux/mm.h | 65 +- include/linux/mman.h | 4 + include/linux/pgtable.h | 14 + include/linux/proc_fs.h | 2 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/siginfo.h | 3 +- include/uapi/asm-generic/unistd.h | 2 +- include/uapi/linux/elf.h | 2 + ipc/shm.c | 2 +- kernel/sys_ni.c | 1 + mm/debug_vm_pgtable.c | 16 +- mm/gup.c | 2 +- mm/huge_memory.c | 7 +- mm/hugetlb.c | 4 +- mm/internal.h | 4 +- mm/memory.c | 5 +- mm/migrate_device.c | 2 +- mm/mmap.c | 10 +- mm/mprotect.c | 2 +- mm/nommu.c | 4 +- mm/userfaultfd.c | 2 +- mm/util.c | 2 +- tools/testing/selftests/x86/Makefile | 2 +- .../testing/selftests/x86/test_shadow_stack.c | 695 ++++++++++++++++++ 116 files changed, 2612 insertions(+), 314 deletions(-) create mode 100644 Documentation/x86/shstk.rst create mode 100644 arch/x86/include/asm/shstk.h create mode 100644 arch/x86/kernel/cet.c create mode 100644 arch/x86/kernel/shstk.c create mode 100644 tools/testing/selftests/x86/test_shadow_stack.c base-commit: eeac8ede17557680855031c6f305ece2378af326 -- 2.17.1
