[PATCH v2 21/24] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

[Bart Van Assche]

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 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index c936fce5b9d7..b4772e5fc176 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -727,6 +727,15 @@ static bool assign_lock_key(struct lockdep_map *lock)
 {
 	unsigned long can_addr, addr = (unsigned long)lock;
 
+	/*
+	 * 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));
+
 	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.rc1.387.gf8505762e3-goog