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 6.0 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: - [01/44] x86: add missing include to sparsemem.h - [02/44] stackdepot: reserve 5 extra bits in depot_stack_handle_t - [03/44] instrumented.h: allow instrumenting both sides of copy_from_user() - [04/44] x86: asm: instrument usercopy in get_user() and __put_user_size() - [05/44] asm-generic: instrument usercopy in cacheflush.h - [10/44] libnvdimm/pfn_dev: increase MAX_STRUCT_PAGE_SIZE 2. KMSAN-related declarations in generic code, KMSAN runtime library, docs and configs: - [06/44] kmsan: add ReST documentation - [07/44] kmsan: introduce __no_sanitize_memory and __no_kmsan_checks - [09/44] x86: kmsan: pgtable: reduce vmalloc space - [11/44] kmsan: add KMSAN runtime core - [13/44] MAINTAINERS: add entry for KMSAN - [25/44] kmsan: add tests for KMSAN - [32/44] objtool: kmsan: list KMSAN API functions as uaccess-safe - [36/44] x86: kmsan: use __msan_ string functions where possible - [44/44] x86: kmsan: enable KMSAN builds for x86 3. Adding hooks from different subsystems to notify KMSAN about memory state changes: - [14/44] mm: kmsan: maintain KMSAN metadata for page - [15/44] mm: kmsan: call KMSAN hooks from SLUB code - [16/44] kmsan: handle task creation and exiting - [17/44] init: kmsan: call KMSAN initialization routines - [18/44] instrumented.h: add KMSAN support - [20/44] kmsan: add iomap support - [21/44] Input: libps2: mark data received in __ps2_command() as initialized - [22/44] dma: kmsan: unpoison DMA mappings - [35/44] x86: kmsan: handle open-coded assembly in lib/iomem.c - [37/43] 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: - [08/44] kmsan: mark noinstr as __no_sanitize_memory - [12/44] kmsan: disable instrumentation of unsupported common kernel code - [19/44] kmsan: unpoison @tlb in arch_tlb_gather_mmu() - [23/44] virtio: kmsan: check/unpoison scatterlist in vring_map_one_sg() - [24/44] kmsan: handle memory sent to/from USB - [26/44] kmsan: disable strscpy() optimization under KMSAN - [27/44] crypto: kmsan: disable accelerated configs under KMSAN - [28/44] kmsan: disable physical page merging in biovec - [29/44] block: kmsan: skip bio block merging logic for KMSAN - [30/44] kcov: kmsan: unpoison area->list in kcov_remote_area_put() - [31/44] security: kmsan: fix interoperability with auto-initialization - [33/44] x86: kmsan: disable instrumentation of unsupported code - [34/44] x86: kmsan: skip shadow checks in __switch_to() - [38/44] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN - [39/44] x86: fs: kmsan: disable CONFIG_DCACHE_WORD_ACCESS - [40/44] x86: kmsan: don't instrument stack walking functions - [41/44] entry: kmsan: introduce kmsan_unpoison_entry_regs() 5. Fixes for bugs detected with CONFIG_KMSAN_CHECK_PARAM_RETVAL: - [42/44] bpf: kmsan: initialize BPF registers with zeroes - [43/44] mm: fs: initialize fsdata passed to write_begin/write_end interface 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. By default, KMSAN enforces conservative checks of most kernel function parameters passed by value (via CONFIG_KMSAN_CHECK_PARAM_RETVAL, which maps to the -fsanitize-memory-param-retval compiler flag). As discussed in [4] and [5], passing uninitialized values as function parameters is considered undefined behavior, therefore KMSAN now reports such cases as errors. Several newly added patches fix known manifestations of these errors. The patchset was generated relative to Linux v6.0-rc4. 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 [6]. A huge thanks goes to the reviewers of the RFC patch series sent to LKML in 2020 ([7]). [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/0000000000002c7abf05e721698d@xxxxxxxxxx/ [4] https://lore.kernel.org/all/20220614144853.3693273-1-glider@xxxxxxxxxx/ [5] https://lore.kernel.org/linux-mm/20220701142310.2188015-45-glider@xxxxxxxxxx/ [6] https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/12604/ [7] https://lore.kernel.org/all/20200325161249.55095-1-glider@xxxxxxxxxx/ Alexander Potapenko (43): stackdepot: reserve 5 extra bits in depot_stack_handle_t instrumented.h: allow instrumenting both sides of copy_from_user() x86: asm: instrument usercopy in get_user() and put_user() asm-generic: instrument usercopy in cacheflush.h kmsan: add ReST documentation kmsan: introduce __no_sanitize_memory and __no_kmsan_checks kmsan: mark noinstr as __no_sanitize_memory x86: kmsan: pgtable: reduce vmalloc space libnvdimm/pfn_dev: increase MAX_STRUCT_PAGE_SIZE kmsan: add KMSAN runtime core kmsan: disable instrumentation of unsupported common kernel code MAINTAINERS: add entry for KMSAN mm: kmsan: maintain KMSAN metadata for page operations mm: kmsan: call KMSAN hooks from SLUB code kmsan: handle task creation and exiting init: kmsan: call KMSAN initialization routines instrumented.h: add KMSAN support kmsan: unpoison @tlb in arch_tlb_gather_mmu() kmsan: add iomap support Input: libps2: mark data received in __ps2_command() as initialized dma: kmsan: unpoison DMA mappings virtio: kmsan: check/unpoison scatterlist in vring_map_one_sg() 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 block: kmsan: skip bio block merging logic for KMSAN kcov: kmsan: 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: disable instrumentation of unsupported code x86: kmsan: skip shadow checks in __switch_to() x86: kmsan: handle open-coded assembly in lib/iomem.c 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: don't instrument stack walking functions entry: kmsan: introduce kmsan_unpoison_entry_regs() bpf: kmsan: initialize BPF registers with zeroes mm: fs: initialize fsdata passed to write_begin/write_end interface x86: kmsan: enable KMSAN builds for x86 Dmitry Vyukov (1): x86: add missing include to sparsemem.h Documentation/dev-tools/index.rst | 1 + Documentation/dev-tools/kmsan.rst | 427 ++++++++++++++++++ MAINTAINERS | 13 + Makefile | 1 + arch/s390/lib/uaccess.c | 3 +- arch/x86/Kconfig | 9 +- arch/x86/boot/Makefile | 1 + arch/x86/boot/compressed/Makefile | 1 + arch/x86/entry/vdso/Makefile | 3 + arch/x86/include/asm/checksum.h | 16 +- arch/x86/include/asm/kmsan.h | 55 +++ arch/x86/include/asm/page_64.h | 7 + arch/x86/include/asm/pgtable_64_types.h | 47 +- arch/x86/include/asm/sparsemem.h | 2 + arch/x86/include/asm/string_64.h | 23 +- arch/x86/include/asm/uaccess.h | 22 +- arch/x86/kernel/Makefile | 2 + arch/x86/kernel/cpu/Makefile | 1 + arch/x86/kernel/dumpstack.c | 6 + arch/x86/kernel/process_64.c | 1 + arch/x86/kernel/unwind_frame.c | 11 + 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/input/serio/libps2.c | 5 +- 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 +- fs/buffer.c | 4 +- fs/namei.c | 2 +- include/asm-generic/cacheflush.h | 14 +- include/linux/compiler-clang.h | 23 + include/linux/compiler-gcc.h | 6 + include/linux/compiler_types.h | 3 +- include/linux/fortify-string.h | 2 + include/linux/highmem.h | 3 + include/linux/instrumented.h | 59 ++- include/linux/kmsan-checks.h | 83 ++++ include/linux/kmsan.h | 330 ++++++++++++++ include/linux/kmsan_types.h | 35 ++ 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/bpf/core.c | 2 +- kernel/dma/mapping.c | 10 +- kernel/entry/common.c | 5 + kernel/exit.c | 2 + kernel/fork.c | 2 + kernel/kcov.c | 7 + kernel/locking/Makefile | 3 +- lib/Kconfig.debug | 1 + lib/Kconfig.kmsan | 62 +++ lib/Makefile | 3 + lib/iomap.c | 44 ++ lib/iov_iter.c | 9 +- lib/stackdepot.c | 29 +- lib/string.c | 8 + lib/usercopy.c | 3 +- mm/Makefile | 1 + mm/filemap.c | 2 +- mm/internal.h | 6 + mm/kasan/common.c | 2 +- mm/kmsan/Makefile | 28 ++ mm/kmsan/core.c | 458 ++++++++++++++++++++ mm/kmsan/hooks.c | 384 +++++++++++++++++ mm/kmsan/init.c | 235 ++++++++++ mm/kmsan/instrumentation.c | 307 +++++++++++++ mm/kmsan/kmsan.h | 208 +++++++++ mm/kmsan/kmsan_test.c | 552 ++++++++++++++++++++++++ mm/kmsan/report.c | 211 +++++++++ mm/kmsan/shadow.c | 294 +++++++++++++ mm/memory.c | 2 + mm/mmu_gather.c | 10 + mm/page_alloc.c | 19 + mm/slab.h | 1 + mm/slub.c | 17 + mm/vmalloc.c | 20 +- scripts/Makefile.kmsan | 8 + scripts/Makefile.lib | 9 + security/Kconfig.hardening | 4 + tools/objtool/check.c | 20 + 94 files changed, 4296 insertions(+), 56 deletions(-) create mode 100644 Documentation/dev-tools/kmsan.rst create mode 100644 arch/x86/include/asm/kmsan.h create mode 100644 include/linux/kmsan-checks.h create mode 100644 include/linux/kmsan.h create mode 100644 include/linux/kmsan_types.h create mode 100644 lib/Kconfig.kmsan create mode 100644 mm/kmsan/Makefile 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 -- 2.37.2.789.g6183377224-goog
