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

commit d7fe143cb115076fed0126ad8cf5ba6c3e575e43 upstream.

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/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 217f7abf2cbfabe74798f24899fc451a8e52d7f7..67964dc4db952ea11d4b88554383ea0ec5946ef9 100644 (file)
--- 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)