The patch titled Subject: mm: kfence: disable KMSAN when checking the canary has been added to the -mm mm-unstable branch. Its filename is mm-kfence-disable-kmsan-when-checking-the-canary.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kfence-disable-kmsan-when-checking-the-canary.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> Subject: mm: kfence: disable KMSAN when checking the canary Date: Thu, 14 Dec 2023 00:24:36 +0100 KMSAN warns about check_canary() accessing the canary. The reason is that, even though set_canary() is properly instrumented and sets shadow, slub explicitly poisons the canary's address range afterwards. Unpoisoning the canary is not the right thing to do: only check_canary() is supposed to ever touch it. Instead, disable KMSAN checks around canary read accesses. Link: https://lkml.kernel.org/r/20231213233605.661251-17-iii@xxxxxxxxxxxxx Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> Tested-by: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Cc: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kfence/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/mm/kfence/core.c~mm-kfence-disable-kmsan-when-checking-the-canary +++ a/mm/kfence/core.c @@ -305,8 +305,14 @@ metadata_update_state(struct kfence_meta WRITE_ONCE(meta->state, next); } +#ifdef CONFIG_KMSAN +#define CHECK_CANARY_ATTRIBUTES noinline __no_kmsan_checks +#else +#define CHECK_CANARY_ATTRIBUTES inline +#endif + /* Check canary byte at @addr. */ -static inline bool check_canary_byte(u8 *addr) +static CHECK_CANARY_ATTRIBUTES bool check_canary_byte(u8 *addr) { struct kfence_metadata *meta; unsigned long flags; @@ -341,7 +347,8 @@ static inline void set_canary(const stru *((u64 *)addr) = KFENCE_CANARY_PATTERN_U64; } -static inline void check_canary(const struct kfence_metadata *meta) +static CHECK_CANARY_ATTRIBUTES void +check_canary(const struct kfence_metadata *meta) { const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE); unsigned long addr = pageaddr; _ Patches currently in -mm which might be from iii@xxxxxxxxxxxxx are ftrace-unpoison-ftrace_regs-in-ftrace_ops_list_func.patch kmsan-make-the-tests-compatible-with-kmsanpanic=1.patch kmsan-disable-kmsan-when-deferred_struct_page_init-is-enabled.patch kmsan-increase-the-maximum-store-size-to-4096.patch kmsan-fix-is_bad_asm_addr-on-arches-with-overlapping-address-spaces.patch kmsan-fix-kmsan_copy_to_user-on-arches-with-overlapping-address-spaces.patch kmsan-remove-a-useless-assignment-from-kmsan_vmap_pages_range_noflush.patch kmsan-remove-an-x86-specific-include-from-kmsanh.patch kmsan-expose-kmsan_get_metadata.patch kmsan-export-panic_on_kmsan.patch kmsan-allow-disabling-kmsan-checks-for-the-current-task.patch kmsan-support-slab_poison.patch kmsan-use-align_down-in-kmsan_get_metadata.patch mm-slub-let-kmsan-access-metadata.patch mm-slub-unpoison-the-memchr_inv-return-value.patch mm-kfence-disable-kmsan-when-checking-the-canary.patch lib-zlib-unpoison-dfltcc-output-buffers.patch kmsan-accept-ranges-starting-with-0-on-s390.patch s390-turn-off-kmsan-for-boot-vdso-and-purgatory.patch s390-use-a-larger-stack-for-kmsan.patch s390-boot-add-the-kmsan-runtime-stub.patch s390-checksum-add-a-kmsan-check.patch s390-cpacf-unpoison-the-results-of-cpacf_trng.patch s390-cpumf-unpoison-stcctm-output-buffer.patch s390-diag-unpoison-diag224-output-buffer.patch s390-ftrace-unpoison-ftrace_regs-in-kprobe_ftrace_handler.patch s390-irqflags-do-not-instrument-arch_local_irq_-with-kmsan.patch s390-mm-define-kmsan-metadata-for-vmalloc-and-modules.patch s390-string-add-kmsan-support.patch s390-traps-unpoison-the-kernel_stack_overflows-pt_regs.patch s390-uaccess-add-kmsan-support-to-put_user-and-get_user.patch s390-unwind-disable-kmsan-checks.patch s390-implement-the-architecture-specific-kmsan-functions.patch kmsan-enable-on-s390.patch