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

Commit-ID:     d7fe143cb115076fed0126ad8cf5ba6c3e575e43
Gitweb:        https://git.kernel.org/tip/d7fe143cb115076fed0126ad8cf5ba6c3e575e43
Author:        Ahmed Ehab <bottaawesome633@gmail.com>
AuthorDate:    Sun, 25 Aug 2024 01:10:30 +03:00
Committer:     Boqun Feng <boqun.feng@gmail.com>
CommitterDate: Thu, 17 Oct 2024 20:07:23 -07:00

locking/lockdep: Avoid creating new name string literals in lockdep_set_subclass()

Syzbot reports a problem that a warning will be triggered while
searching a lock class in look_up_lock_class().

The cause of the issue is that a new name is created and used by
lockdep_set_subclass() instead of using the existing one. This results
in a lock instance has a different name pointer than previous registered
one stored in lock class, and WARN_ONCE() is triggered because of that
in look_up_lock_class().

To fix this, change lockdep_set_subclass() to use the existing name
instead of a new one. Hence, no new name will be created by
lockdep_set_subclass(). Hence, the warning is avoided.

[boqun: Reword the commit log to state the correct issue]

Reported-by: <syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com>
Fixes: de8f5e4f2dc1f ("lockdep: Introduce wait-type checks")
Cc: stable@vger.kernel.org
Signed-off-by: Ahmed Ehab <bottaawesome633@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/lkml/20240824221031.7751-1-bottaawesome633@gmail.com/
---
 include/linux/lockdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 217f7ab..67964dc 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -173,7 +173,7 @@ static inline void lockdep_init_map(struct lockdep_map *lock, const char *name,
 			      (lock)->dep_map.lock_type)
 
 #define lockdep_set_subclass(lock, sub)					\
-	lockdep_init_map_type(&(lock)->dep_map, #lock, (lock)->dep_map.key, sub,\
+	lockdep_init_map_type(&(lock)->dep_map, (lock)->dep_map.name, (lock)->dep_map.key, sub,\
 			      (lock)->dep_map.wait_type_inner,		\
 			      (lock)->dep_map.wait_type_outer,		\
 			      (lock)->dep_map.lock_type)