locking/lockdep: Prevent abuse of lockdep subclass

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

Posted by Waiman Long 10 months ago

As I have seen 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.

Signed-off-by: Waiman Long <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 58d78a33ac65..3fb79d8fecdf 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];
 	/*
-- 
2.48.1

Re: [PATCH] locking/lockdep: Prevent abuse of lockdep subclass

Posted by Boqun Feng 9 months, 1 week ago

On Wed, Apr 09, 2025 at 10:37:51AM -0400, Waiman Long wrote:
> As I have seen 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.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>

Queued for 6.16, thanks!

Regards,
Boqun

> ---
>  kernel/locking/lockdep.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 58d78a33ac65..3fb79d8fecdf 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];
>  	/*
> -- 
> 2.48.1
>