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

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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: de8f5e4f2d ("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/
This commit is contained in:
Ahmed Ehab 2024-08-25 01:10:30 +03:00 committed by Boqun Feng
parent 0784181b44
commit d7fe143cb1
1 changed files with 1 additions and 1 deletions
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2
include/linux/lockdep.h
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@ -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)