[tip: locking/core] locking/lockdep: Prevent abuse of lockdep subclass

["tip-bot2 for Waiman Long" <tip-bot2@linutronix.de>]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     6a1a219f535a437eb12a06d8cef2518e58654beb
Gitweb:        https://git.kernel.org/tip/6a1a219f535a437eb12a06d8cef2518e58654beb
Author:        Waiman Long <longman@redhat.com>
AuthorDate:    Mon, 05 May 2025 21:20:48 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 06 May 2025 18:34:35 +02:00

locking/lockdep: Prevent abuse of lockdep subclass

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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20250506042049.50060-3-boqun.feng@gmail.com
---
 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 546e928..050dbe9 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];
 	/*