[PATCH v4 00/17] Add support for Clang CFI

From: Sami Tolvanen
Date: Wed Mar 31 2021 - 17:28:13 EST

This series adds support for Clang's Control-Flow Integrity (CFI)
checking. With CFI, the compiler injects a runtime check before each
indirect function call to ensure the target is a valid function with
the correct static type. This restricts possible call targets and
makes it more difficult for an attacker to exploit bugs that allow the
modification of stored function pointers. For more details, see:

https://clang.llvm.org/docs/ControlFlowIntegrity.html

The first patch contains build system changes and error handling,
and implements support for cross-module indirect call checking. The
remaining patches address issues caused by the compiler
instrumentation. These include fixing known type mismatches, as well
as issues with address space confusion and cross-module function
address equality.

These patches add support only for arm64, but I'll post patches also
for x86_64 after we address the remaining issues there, including
objtool support.

You can also pull this series from

https://github.com/samitolvanen/linux.git cfi-v4

---
Changes in v4:
- Per Mark's suggestion, dropped __pa_function() and renamed
__va_function() to function_nocfi().
- Added a comment to function_nocfi() to explain what it does.
- Updated the psci patch to use an intermediate variable for
the physical address for clarity.

Changes in v3:
- Added a patch to change list_sort() callers treewide to use
const pointers instead of simply removing the internal casts.
- Changed cleanup_symbol_name() to return bool.
- Changed module.lds.S to drop the .eh_frame section only with
CONFIG_CFI_CLANG.
- Switched to synchronize_rcu() in update_shadow().

Changes in v2:
- Fixed .text merging in module.lds.S.
- Added WARN_ON_FUNCTION_MISMATCH() and changed kernel/thread.c
and kernel/workqueue.c to use the macro instead.


Sami Tolvanen (17):
add support for Clang CFI
cfi: add __cficanonical
mm: add generic function_nocfi macro
module: ensure __cfi_check alignment
workqueue: use WARN_ON_FUNCTION_MISMATCH
kthread: use WARN_ON_FUNCTION_MISMATCH
kallsyms: strip ThinLTO hashes from static functions
bpf: disable CFI in dispatcher functions
treewide: Change list_sort to use const pointers
lkdtm: use function_nocfi
psci: use function_nocfi for cpu_resume
arm64: implement function_nocfi
arm64: use function_nocfi with __pa_symbol
arm64: add __nocfi to functions that jump to a physical address
arm64: add __nocfi to __apply_alternatives
KVM: arm64: Disable CFI for nVHE
arm64: allow CONFIG_CFI_CLANG to be selected

Makefile | 17 +
arch/Kconfig | 45 +++
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/memory.h | 15 +
arch/arm64/include/asm/mmu_context.h | 4 +-
arch/arm64/kernel/acpi_parking_protocol.c | 3 +-
arch/arm64/kernel/alternative.c | 4 +-
arch/arm64/kernel/cpu-reset.h | 10 +-
arch/arm64/kernel/cpufeature.c | 4 +-
arch/arm64/kernel/psci.c | 3 +-
arch/arm64/kernel/smp_spin_table.c | 3 +-
arch/arm64/kvm/hyp/nvhe/Makefile | 6 +-
arch/arm64/kvm/vgic/vgic-its.c | 8 +-
arch/arm64/kvm/vgic/vgic.c | 3 +-
block/blk-mq-sched.c | 3 +-
block/blk-mq.c | 3 +-
drivers/acpi/nfit/core.c | 3 +-
drivers/acpi/numa/hmat.c | 3 +-
drivers/clk/keystone/sci-clk.c | 4 +-
drivers/firmware/psci/psci.c | 7 +-
drivers/gpu/drm/drm_modes.c | 3 +-
drivers/gpu/drm/i915/gt/intel_engine_user.c | 3 +-
drivers/gpu/drm/i915/gvt/debugfs.c | 2 +-
drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 3 +-
drivers/gpu/drm/radeon/radeon_cs.c | 4 +-
.../hw/usnic/usnic_uiom_interval_tree.c | 3 +-
drivers/interconnect/qcom/bcm-voter.c | 2 +-
drivers/md/raid5.c | 3 +-
drivers/misc/lkdtm/usercopy.c | 2 +-
drivers/misc/sram.c | 4 +-
drivers/nvme/host/core.c | 3 +-
.../controller/cadence/pcie-cadence-host.c | 3 +-
drivers/spi/spi-loopback-test.c | 3 +-
fs/btrfs/raid56.c | 3 +-
fs/btrfs/tree-log.c | 3 +-
fs/btrfs/volumes.c | 3 +-
fs/ext4/fsmap.c | 4 +-
fs/gfs2/glock.c | 3 +-
fs/gfs2/log.c | 2 +-
fs/gfs2/lops.c | 3 +-
fs/iomap/buffered-io.c | 3 +-
fs/ubifs/gc.c | 7 +-
fs/ubifs/replay.c | 4 +-
fs/xfs/scrub/bitmap.c | 4 +-
fs/xfs/xfs_bmap_item.c | 4 +-
fs/xfs/xfs_buf.c | 6 +-
fs/xfs/xfs_extent_busy.c | 4 +-
fs/xfs/xfs_extent_busy.h | 3 +-
fs/xfs/xfs_extfree_item.c | 4 +-
fs/xfs/xfs_refcount_item.c | 4 +-
fs/xfs/xfs_rmap_item.c | 4 +-
include/asm-generic/bug.h | 16 +
include/asm-generic/vmlinux.lds.h | 20 +-
include/linux/bpf.h | 4 +-
include/linux/cfi.h | 41 +++
include/linux/compiler-clang.h | 3 +
include/linux/compiler_types.h | 8 +
include/linux/init.h | 6 +-
include/linux/list_sort.h | 7 +-
include/linux/mm.h | 10 +
include/linux/module.h | 13 +-
include/linux/pci.h | 4 +-
init/Kconfig | 2 +-
kernel/Makefile | 4 +
kernel/cfi.c | 329 ++++++++++++++++++
kernel/kallsyms.c | 55 ++-
kernel/kthread.c | 3 +-
kernel/module.c | 43 +++
kernel/workqueue.c | 2 +-
lib/list_sort.c | 17 +-
lib/test_list_sort.c | 3 +-
net/tipc/name_table.c | 4 +-
scripts/Makefile.modfinal | 2 +-
scripts/module.lds.S | 20 +-
74 files changed, 759 insertions(+), 112 deletions(-)
create mode 100644 include/linux/cfi.h
create mode 100644 kernel/cfi.c


base-commit: d19cc4bfbff1ae72c3505a00fb8ce0d3fa519e6c
--
2.31.0.291.g576ba9dcdaf-goog