[GIT PULL] x86/shstk for 6.4

Dave Hansen
2023-04-24T21:21:42Z

Hi Linus,

Please pull x86/shstk for 6.4. This is the long-awaited Shadow Stack
support. It is the most highly desired hardware security feature in a
long time. Both AMD and Intel have (compatible) implementations. It
has been present on the Intel side since the 11th-gen CPUs, but it had a
few stumbles on the way and is a bit tardy.

The trickiest part of this whole thing (IMNHO) was that shadow stacks
exist in a permission grey area. A shadow stack PTE literally says
Write=0, but some instructions _can_ write to it. The PTEs also can't
be read-only so they can't be COW'd. They are oddballs.

The Write=0,Dirty=1 PTE permissions also mean that the dirty bit can not
be used as freely as before. Those two things combine to create a fair
amount of PTE management churn.

A few more things you should know:

1. There is a non-trivial amount of core mm churn. It has acks from
mm folks and I hope it's no surprise to Andrew. These add a VMA
argument to pte_mkwrite(). There is a new user in Andrew's
pile[1*] which will need to get fixed up[2*] before this gets
merged with the mm tree.
2. There has been an unusual snarl of userspace compatibility issues
with shadow stacks [3*]. While the move to new arch_prctl() values
helped, we can still envision scenarios where this old code might
bite us. The plan is try to ban any problematic apps from using
shadow stack if anything comes up in practice. We should obviously
be on the lookout for these.
3. This conflicts with the LAM code which is coming in x86/mm. I'll
discuss the resolution when I send x86/mm.

[1*] 717f95b494ac36 ("mm: don't check VMA write permissions if the PTE/PMD indicates write permissions")
[2*] https://lore.kernel.org/all/20230419182136.112974-1-broonie@kernel.org/
[3*] https://lore.kernel.org/lkml/CAHk-=wgP5mk3poVeejw16Asbid0ghDt4okHnWaWKLBkRhQntRA@mail.gmail.com/

--

The following changes since commit eeac8ede17557680855031c6f305ece2378af326:

Linux 6.3-rc2 (2023-03-12 16:36:44 -0700)

are available in the Git repository at:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git tags/x86_shstk_for_6.4

for you to fetch changes up to 11c95c77eef6d56c1ef9f55d8afd83ceb6d99996:

x86/shstk: Enforce only whole copies for ssp_set() (2023-03-27 17:55:51 -0700)

----------------------------------------------------------------
Add x86 shadow stack support. Includes:
* New arch_prctl() ABI for enable/disable/lock/debug
* Plumbing to deal with the new Write=0,Dirty=1 PTE permissions
* Core mm changes that allow some PTE write functions to take
a VMA so they can tell if the VMA is for a shadow stack
* Normal old selftest and documentation

----------------------------------------------------------------
Mike Rapoport (1):
x86/shstk: Add ARCH_SHSTK_UNLOCK

Rick Edgecombe (37):
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
x86/shstk: Enforce only whole copies for ssp_set()

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 | 81 +++
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 +-
tools/testing/selftests/x86/test_shadow_stack.c | 695 ++++++++++++++++++++++++
116 files changed, 2615 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