[PATCH v8 00/40] Shadow stacks for userspace
From: Rick Edgecombe
Date: Sat Mar 18 2023 - 20:16:05 EST
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