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[v3,16/34] mm: kfence: Disable KMSAN when checking the canary

Message ID 20231213233605.661251-17-iii@linux.ibm.com (mailing list archive)
State Handled Elsewhere
Headers show
Series kmsan: Enable on s390 | expand

Commit Message

Ilya Leoshkevich Dec. 13, 2023, 11:24 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
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 mbox series

Patch

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 3872528d0963..96138e704c5a 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;