KernelMemorySanitizer (KMSAN) is a detector of errors related to uses of uninitialized memory. It relies on compile-time Clang instrumentation (similar to MSan in the userspace [1]) and tracks the state of every bit of kernel memory, being able to report an error if uninitialized value is used in a condition, dereferenced, or escapes to userspace, USB or DMA. KMSAN has reported more than 300 bugs in the past few years (recently fixed bugs: [2]), most of them with the help of syzkaller. Such bugs keep getting introduced into the kernel despite new compiler warnings and other analyses (the 5.16 cycle already resulted in several KMSAN-reported bugs, e.g. [3]). Mitigations like total stack and heap initialization are unfortunately very far from being deployable. The proposed patchset contains KMSAN runtime implementation together with small changes to other subsystems needed to make KMSAN work. The latter changes fall into several categories: 1. Changes and refactorings of existing code required to add KMSAN: - [1/43] arch/x86: add missing include to sparsemem.h - [2/43] stackdepot: reserve 5 extra bits in depot_stack_handle_t - [3/43] kasan: common: adapt to the new prototype of __stack_depot_save() - [4/43] instrumented.h: allow instrumenting both sides of copy_from_user() - [5/43] asm: x86: instrument usercopy in get_user() and __put_user_size() - [6/43] asm-generic: instrument usercopy in cacheflush.h - [7/43] compiler_attributes.h: add __disable_sanitizer_instrumentation - [11/43] libnvdimm/pfn_dev: increase MAX_STRUCT_PAGE_SIZE - [12/43] kcsan: clang: retire CONFIG_KCSAN_KCOV_BROKEN 2. KMSAN-related declarations in generic code, KMSAN runtime library, docs and configs: - [8/43] kmsan: add ReST documentation - [9/43] kmsan: introduce __no_sanitize_memory and __no_kmsan_checks - [10/43] kmsan: pgtable: reduce vmalloc space - [13/43] kmsan: add KMSAN runtime core - [14/43] MAINTAINERS: add entry for KMSAN - [30/43] kmsan: add tests for KMSAN - [35/43] x86: kmsan: use __msan_ string functions where possible. - [42/43] objtool: kmsan: list KMSAN API functions as uaccess-safe - [43/43] x86: kmsan: enable KMSAN builds for x86 3. Adding hooks from different subsystems to notify KMSAN about memory state changes: - [15/43] kmsan: mm: maintain KMSAN metadata for page operations - [16/43] kmsan: mm: call KMSAN hooks from SLUB code - [17/43] kmsan: handle task creation and exiting - [19/43] kmsan: init: call KMSAN initialization routines - [20/43] instrumented.h: add KMSAN support - [26/43] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() - [27/43] x86: kmsan: add iomem support - [28/43] kmsan: dma: unpoison DMA mappings - [29/43] kmsan: handle memory sent to/from USB - [36/43] x86: kmsan: sync metadata pages on page fault 4. Changes that prevent false reports by explicitly initializing memory, disabling optimized code that may trick KMSAN, selectively skipping instrumentation: - [18/43] kmsan: unpoison @tlb in arch_tlb_gather_mmu() - [22/43] kmsan: initialize the output of READ_ONCE_NOCHECK() - [23/43] kmsan: make READ_ONCE_TASK_STACK() return initialized values - [24/43] kmsan: disable KMSAN instrumentation for certain kernel parts - [25/43] kmsan: skip shadow checks in files doing context switches - [31/43] kmsan: disable strscpy() optimization under KMSAN - [32/43] crypto: kmsan: disable accelerated configs under KMSAN - [33/43] kmsan: disable physical page merging in biovec - [34/43] kmsan: block: skip bio block merging logic for KMSAN - [37/43] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN - [38/43] x86: fs: kmsan: disable CONFIG_DCACHE_WORD_ACCESS - [40/43] kmsan: kcov: unpoison area->list in kcov_remote_area_put() - [41/43] security: kmsan: fix interoperability with auto-initialization 5. Noinstr handling: - [21/43] kmsan: mark noinstr as __no_sanitize_memory - [39/43] x86: kmsan: handle register passing from uninstrumented code This patchset allows one to boot and run a defconfig+KMSAN kernel on a QEMU without known false positives. It however doesn't guarantee there are no false positives in drivers of certain devices or less tested subsystems, although KMSAN is actively tested on syzbot with a large config. The patchset was generated relative to Linux v5.16-rc5. The most up-to-date KMSAN tree currently resides at https://github.com/google/kmsan/. One may find it handy to review these patches in Gerrit: https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/1081 A huge thanks goes to the reviewers of the RFC patch series sent to LKML last year (https://lore.kernel.org/all/20200325161249.55095-1-glider@xxxxxxxxxx/). [1] https://clang.llvm.org/docs/MemorySanitizer.html [2] https://syzkaller.appspot.com/upstream/fixed?manager=ci-upstream-kmsan-gce [3] https://lore.kernel.org/all/20211126124746.761278-1-glider@xxxxxxxxxx/ Alexander Potapenko (42): stackdepot: reserve 5 extra bits in depot_stack_handle_t kasan: common: adapt to the new prototype of __stack_depot_save() instrumented.h: allow instrumenting both sides of copy_from_user() asm: x86: instrument usercopy in get_user() and __put_user_size() asm-generic: instrument usercopy in cacheflush.h compiler_attributes.h: add __disable_sanitizer_instrumentation kmsan: add ReST documentation kmsan: introduce __no_sanitize_memory and __no_kmsan_checks kmsan: pgtable: reduce vmalloc space libnvdimm/pfn_dev: increase MAX_STRUCT_PAGE_SIZE kcsan: clang: retire CONFIG_KCSAN_KCOV_BROKEN kmsan: add KMSAN runtime core MAINTAINERS: add entry for KMSAN kmsan: mm: maintain KMSAN metadata for page operations kmsan: mm: call KMSAN hooks from SLUB code kmsan: handle task creation and exiting kmsan: unpoison @tlb in arch_tlb_gather_mmu() kmsan: init: call KMSAN initialization routines instrumented.h: add KMSAN support kmsan: mark noinstr as __no_sanitize_memory kmsan: initialize the output of READ_ONCE_NOCHECK() kmsan: make READ_ONCE_TASK_STACK() return initialized values kmsan: disable KMSAN instrumentation for certain kernel parts kmsan: skip shadow checks in files doing context switches kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() x86: kmsan: add iomem support kmsan: dma: unpoison DMA mappings kmsan: handle memory sent to/from USB kmsan: add tests for KMSAN kmsan: disable strscpy() optimization under KMSAN crypto: kmsan: disable accelerated configs under KMSAN kmsan: disable physical page merging in biovec kmsan: block: skip bio block merging logic for KMSAN x86: kmsan: use __msan_ string functions where possible. x86: kmsan: sync metadata pages on page fault x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN x86: fs: kmsan: disable CONFIG_DCACHE_WORD_ACCESS x86: kmsan: handle register passing from uninstrumented code kmsan: kcov: unpoison area->list in kcov_remote_area_put() security: kmsan: fix interoperability with auto-initialization objtool: kmsan: list KMSAN API functions as uaccess-safe x86: kmsan: enable KMSAN builds for x86 Dmitry Vyukov (1): arch/x86: add missing include to sparsemem.h Documentation/dev-tools/index.rst | 1 + Documentation/dev-tools/kmsan.rst | 411 ++++++++++++++++++++++ MAINTAINERS | 12 + Makefile | 1 + arch/x86/Kconfig | 9 +- arch/x86/boot/Makefile | 1 + arch/x86/boot/compressed/Makefile | 1 + arch/x86/entry/common.c | 2 + arch/x86/entry/vdso/Makefile | 3 + arch/x86/include/asm/checksum.h | 16 +- arch/x86/include/asm/idtentry.h | 5 + arch/x86/include/asm/page_64.h | 13 + arch/x86/include/asm/pgtable_64_types.h | 41 ++- arch/x86/include/asm/sparsemem.h | 2 + arch/x86/include/asm/string_64.h | 23 +- arch/x86/include/asm/uaccess.h | 7 + arch/x86/include/asm/unwind.h | 23 +- arch/x86/kernel/Makefile | 6 + arch/x86/kernel/cpu/Makefile | 1 + arch/x86/kernel/cpu/mce/core.c | 1 + arch/x86/kernel/kvm.c | 1 + arch/x86/kernel/nmi.c | 1 + arch/x86/kernel/sev.c | 2 + arch/x86/kernel/traps.c | 7 + arch/x86/lib/Makefile | 2 + arch/x86/lib/iomem.c | 5 + arch/x86/mm/Makefile | 2 + arch/x86/mm/fault.c | 23 +- arch/x86/mm/init_64.c | 2 +- arch/x86/mm/ioremap.c | 3 + arch/x86/realmode/rm/Makefile | 1 + block/bio.c | 2 + block/blk.h | 7 + crypto/Kconfig | 30 ++ drivers/firmware/efi/libstub/Makefile | 1 + drivers/net/Kconfig | 1 + drivers/nvdimm/nd.h | 2 +- drivers/nvdimm/pfn_devs.c | 2 +- drivers/usb/core/urb.c | 2 + drivers/virtio/virtio_ring.c | 10 +- include/asm-generic/cacheflush.h | 9 +- include/asm-generic/rwonce.h | 5 +- include/linux/compiler-clang.h | 23 ++ include/linux/compiler-gcc.h | 6 + include/linux/compiler_attributes.h | 18 + include/linux/compiler_types.h | 3 +- include/linux/fortify-string.h | 2 + include/linux/highmem.h | 3 + include/linux/instrumented.h | 26 +- include/linux/kmsan-checks.h | 123 +++++++ include/linux/kmsan.h | 365 +++++++++++++++++++ include/linux/mm_types.h | 12 + include/linux/sched.h | 5 + include/linux/stackdepot.h | 8 + include/linux/uaccess.h | 19 +- init/main.c | 3 + kernel/Makefile | 1 + kernel/dma/mapping.c | 9 +- kernel/entry/common.c | 3 + kernel/exit.c | 2 + kernel/fork.c | 2 + kernel/kcov.c | 7 + kernel/locking/Makefile | 3 +- kernel/sched/Makefile | 4 + lib/Kconfig.debug | 1 + lib/Kconfig.kcsan | 11 - lib/Kconfig.kmsan | 34 ++ lib/Makefile | 1 + lib/iomap.c | 40 +++ lib/iov_iter.c | 9 +- lib/stackdepot.c | 29 +- lib/string.c | 8 + lib/usercopy.c | 3 +- mm/Makefile | 1 + mm/kasan/common.c | 2 +- mm/kmsan/Makefile | 26 ++ mm/kmsan/annotations.c | 28 ++ mm/kmsan/core.c | 427 +++++++++++++++++++++++ mm/kmsan/hooks.c | 400 +++++++++++++++++++++ mm/kmsan/init.c | 238 +++++++++++++ mm/kmsan/instrumentation.c | 233 +++++++++++++ mm/kmsan/kmsan.h | 197 +++++++++++ mm/kmsan/kmsan_test.c | 444 ++++++++++++++++++++++++ mm/kmsan/report.c | 210 +++++++++++ mm/kmsan/shadow.c | 332 ++++++++++++++++++ mm/memory.c | 2 + mm/mmu_gather.c | 10 + mm/page_alloc.c | 18 + mm/slab.h | 1 + mm/slub.c | 26 +- mm/vmalloc.c | 20 +- scripts/Makefile.kmsan | 1 + scripts/Makefile.lib | 9 + security/Kconfig.hardening | 4 + tools/objtool/check.c | 19 + 95 files changed, 4062 insertions(+), 68 deletions(-) create mode 100644 Documentation/dev-tools/kmsan.rst create mode 100644 include/linux/kmsan-checks.h create mode 100644 include/linux/kmsan.h create mode 100644 lib/Kconfig.kmsan create mode 100644 mm/kmsan/Makefile create mode 100644 mm/kmsan/annotations.c create mode 100644 mm/kmsan/core.c create mode 100644 mm/kmsan/hooks.c create mode 100644 mm/kmsan/init.c create mode 100644 mm/kmsan/instrumentation.c create mode 100644 mm/kmsan/kmsan.h create mode 100644 mm/kmsan/kmsan_test.c create mode 100644 mm/kmsan/report.c create mode 100644 mm/kmsan/shadow.c create mode 100644 scripts/Makefile.kmsan -- 2.34.1.173.g76aa8bc2d0-goog
