[PATCH v5 12/15] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

From: Bart Van Assche
Date: Mon Dec 17 2018 - 16:31:17 EST


Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
kernel/locking/lockdep.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index d411660572e1..1eb03a29f2c2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -743,6 +743,17 @@ static bool assign_lock_key(struct lockdep_map *lock)
{
unsigned long can_addr, addr = (unsigned long)lock;

+#ifdef __KERNEL__
+ /*
+ * lockdep_free_key_range() assumes that struct lock_class_key
+ * objects do not overlap. Since we use the address of lock
+ * objects as class key for static objects, check whether the
+ * size of lock_class_key objects does not exceed the size of
+ * the smallest lock object.
+ */
+ BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
+#endif
+
if (__is_kernel_percpu_address(addr, &can_addr))
lock->key = (void *)can_addr;
else if (__is_module_percpu_address(addr, &can_addr))
--
2.20.0.405.gbc1bbc6f85-goog