[PATCH v5 18/37] mm: kfence: Disable KMSAN when checking the canary
From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: 2024-06-19 15:46:13
Also in:
linux-mm, linux-s390, lkml
Subsystem:
kfence, memory management, the rest · Maintainers:
Alexander Potapenko, Marco Elver, Andrew Morton, Linus Torvalds
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. Reviewed-by: Alexander Potapenko <glider@google.com> Tested-by: Alexander Potapenko <glider@google.com> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- mm/kfence/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 964b8482275b..83f8e78827c0 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c@@ -305,8 +305,14 @@ metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state nex 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 struct kfence_metadata *meta) *((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;
--
2.45.1