In certain cases (e.g. when handling a softirq)
__msan_instrument_asm_store(&var, sizeof(var)) may be called with
from within KMSAN runtime, but later the value of @var is used
with !kmsan_in_runtime(), leading to false positives.
Because kmsan_internal_unpoison_memory() doesn't take locks, it should
be fine to call it without kmsan_in_runtime() checks, which fixes the
mentioned false positives.
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
mm/kmsan/instrumentation.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/kmsan/instrumentation.c b/mm/kmsan/instrumentation.c
index 271f135f97a16..770fe02904f36 100644
--- a/mm/kmsan/instrumentation.c
+++ b/mm/kmsan/instrumentation.c
@@ -81,12 +81,16 @@ DECLARE_METADATA_PTR_GETTER(8);
* Handle a memory store performed by inline assembly. KMSAN conservatively
* attempts to unpoison the outputs of asm() directives to prevent false
* positives caused by missed stores.
+ *
+ * __msan_instrument_asm_store() may be called for inline assembly code when
+ * entering or leaving IRQ. We omit the check for kmsan_in_runtime() to ensure
+ * the memory written to in these cases is also marked as initialized.
*/
void __msan_instrument_asm_store(void *addr, uintptr_t size)
{
unsigned long ua_flags;
- if (!kmsan_enabled || kmsan_in_runtime())
+ if (!kmsan_enabled)
return;
ua_flags = user_access_save();
@@ -103,10 +107,8 @@ void __msan_instrument_asm_store(void *addr, uintptr_t size)
user_access_restore(ua_flags);
return;
}
- kmsan_enter_runtime();
/* Unpoisoning the memory on best effort. */
kmsan_internal_unpoison_memory(addr, size, /*checked*/ false);
- kmsan_leave_runtime();
user_access_restore(ua_flags);
}
EXPORT_SYMBOL(__msan_instrument_asm_store);
--
2.38.1.584.g0f3c55d4c2-goog
