[PATCH 2/3] locking/lockdep: Prevent abuse of lockdep subclass

[Boqun Feng <boqun.feng@gmail.com>]

From: Waiman Long <longman@redhat.com>

To catch the code trying to use a subclass value >=
MAX_LOCKDEP_SUBCLASSES (8), add a DEBUG_LOCKS_WARN_ON() statement to
notify the users that such a large value is not allowed.

[boqun: Reword the commit log with a more objective tone]

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20250409143751.2010391-1-longman@redhat.com
---
 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ff2ce90a87bc..58883c8375d1 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5101,6 +5101,9 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 		lockevent_inc(lockdep_nocheck);
 	}
 
+	if (DEBUG_LOCKS_WARN_ON(subclass >= MAX_LOCKDEP_SUBCLASSES))
+		return 0;
+
 	if (subclass < NR_LOCKDEP_CACHING_CLASSES)
 		class = lock->class_cache[subclass];
 	/*
-- 
2.39.5 (Apple Git-154)