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[v4,17/35] mm: kfence: Disable KMSAN when checking the canary

Message ID 20240613153924.961511-18-iii@linux.ibm.com (mailing list archive)
State New
Headers show
Series kmsan: Enable on s390 | expand

Commit Message

Ilya Leoshkevich June 13, 2024, 3:34 p.m. UTC
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

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(-)
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diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 964b8482275b..cce330d5b797 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);
+#define CHECK_CANARY_ATTRIBUTES noinline __no_kmsan_checks
 /* 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)
+check_canary(const struct kfence_metadata *meta)
 	const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE);
 	unsigned long addr = pageaddr;