Checking if the lockdep_map->name will change when setting the subclass. It shouldn't change so that the lock class and subclass will have the same name

Reported-by: syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com Fixes: fd5e3f5fe27 Cc: stable@vger.kernel.org Signed-off-by: botta633 bottaawesome633@gmail.com --- lib/locking-selftest.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 6f6a5fc85b42..1d7885205f36 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -2710,12 +2710,24 @@ static void local_lock_3B(void)

}

+static void class_subclass_X1_name(void) +{ + const char *name_before_subclass = rwsem_X1.dep_map.name; + const char *name_after_subclass; + + WARN_ON(!rwsem_X1.dep_map.name); + lockdep_set_subclass(&rwsem_X1, 1); + WARN_ON(name_before_subclass != name_after_subclass); +} + static void local_lock_tests(void) { printk(" --------------------------------------------------------------------------\n"); printk(" | local_lock tests |\n"); printk(" ---------------------\n");

+ init_class_X(&lock_X1, &rwlock_X1, &mutex_X1, &rwsem_X1); + print_testname("local_lock inversion 2"); dotest(local_lock_2, SUCCESS, LOCKTYPE_LL); pr_cont("\n"); @@ -2727,6 +2739,10 @@ static void local_lock_tests(void) print_testname("local_lock inversion 3B"); dotest(local_lock_3B, FAILURE, LOCKTYPE_LL); pr_cont("\n"); + + print_testname("Class and subclass"); + dotest(class_subclass_X1_name, SUCCESS, LOCKTYPE_RWSEM); + pr_cont("\n"); }

static void hardirq_deadlock_softirq_not_deadlock(void)

On 7/14/24 01:14, botta633 wrote:

From: Ahmed Ehab bottaawesome633@gmail.com

Preventing lockdep_set_subclass from creating a new instance of the string literal. Hence, we will always have the same class->name among parent and subclasses. This prevents kernel panics when looking up a lock class while comparing class locks and class names.

Reported-by: syzbot+7f4a6f7f7051474e40ad@syzkaller.appspotmail.com Fixes: fd5e3f5fe27 Cc: stable@vger.kernel.org Signed-off-by: Ahmed Ehab 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 08b0d1d9d78b..df8fa5929de7 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)

ext4 is a filesystem. It has nothing to do with locking/lockdep. Could you resend the patches with the proper prefix of "lockdep:" or "locking/lockdep:"?

Thanks, Longman