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 main changes in this version are the MM suggestions by David Hildenbrand to have pte_mkwrite() take a vma, and rename _PAGE_COW. The former is split over three patches: mm: Introduce pte_mkwrite_kernel() s390/mm: Introduce pmd_mkwrite_kernel() mm: Make pte_mkwrite() take a VMA With these changes, and an adjustment to "mm: Warn on shadow stack memory in wrong vma", references to "shstk" are now only in x86 arch code, hopefully addressing Andrew Morton's concerns. There are still a couple VM_SHADOW_STACK references, which seems to be in keeping with the treatment of other VM_HIGH_ARCH flags. If other shadow stack implementations end up with identical logic, it can easily be refactored at that point. There was also some more feedback from Boris which was incorporated. I left tested-by tags in place per discussion with testers. Testers, please retest. Previous version [1]. Thanks, Rick [0] https://lore.kernel.org/lkml/20220130211838.8382-1-rick.p.edgecombe@xxxxxxxxx/ [1] https://lore.kernel.org/lkml/20230119212317.8324-1-rick.p.edgecombe@xxxxxxxxx/ Kirill A. Shutemov (1): x86: Introduce userspace API for shadow stack Mike Rapoport (1): x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe (19): x86/fpu: Add helper for modifying xstate x86: Move control protection handler to separate 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: Start actually marking _PAGE_SAVED_DIRTY x86/mm: Teach pte_mkwrite() about stack memory 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/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/fpu: Add helper for initing features x86/shstk: Add ARCH_SHSTK_STATUS Yu-cheng Yu (20): 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/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 x86/mm: Update ptep/pmdp_set_wrprotect() for _PAGE_SAVED_DIRTY mm: Move VM_UFFD_MINOR_BIT from 37 to 38 mm: Introduce VM_SHADOW_STACK for shadow stack memory x86/mm: Check shadow stack page fault errors mm: Add guard pages around a shadow stack. mm/mmap: Add shadow stack pages to memory accounting mm: Re-introduce vm_flags to do_mmap() 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: Add PTRACE interface for shadow stack Documentation/filesystems/proc.rst | 1 + Documentation/mm/arch_pgtable_helpers.rst | 9 +- Documentation/x86/index.rst | 1 + Documentation/x86/shstk.rst | 176 +++++ 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/msr.h | 11 + arch/x86/include/asm/pgtable.h | 322 ++++++++- arch/x86/include/asm/pgtable_types.h | 71 +- arch/x86/include/asm/processor.h | 8 + arch/x86/include/asm/shstk.h | 40 ++ 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 | 59 +- arch/x86/kernel/fpu/regset.c | 86 +++ arch/x86/kernel/fpu/xstate.c | 148 ++-- arch/x86/kernel/fpu/xstate.h | 6 + arch/x86/kernel/idt.c | 2 +- arch/x86/kernel/process.c | 18 +- arch/x86/kernel/process_64.c | 9 +- arch/x86/kernel/ptrace.c | 12 + arch/x86/kernel/shstk.c | 491 +++++++++++++ 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 | 38 + 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 | 46 +- 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/memory.c | 5 +- mm/migrate_device.c | 2 +- mm/mmap.c | 12 +- mm/mprotect.c | 2 +- mm/nommu.c | 4 +- mm/userfaultfd.c | 2 +- mm/util.c | 2 +- tools/testing/selftests/x86/Makefile | 4 +- .../testing/selftests/x86/test_shadow_stack.c | 676 ++++++++++++++++++ 117 files changed, 2671 insertions(+), 324 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 -- 2.17.1
