linux-kernel - [PATCH v2 16/24] locking/lockdep: Retain the class key and name while freeing a lock class

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Message-Id: <20181204002833.55452-17-bvanassche@acm.org>
Date:   Mon,  3 Dec 2018 16:28:25 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     mingo@...hat.com
Cc:     peterz@...radead.org, tj@...nel.org, longman@...hat.com,
        johannes.berg@...el.com, linux-kernel@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        Johannes Berg <johannes@...solutions.net>
Subject: [PATCH v2 16/24] locking/lockdep: Retain the class key and name while freeing a lock class

The next patch in this series uses the class name in code that
detects lock class use-after-free. Hence retain the class name for
lock classes that are being freed.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Johannes Berg <johannes@...solutions.net>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 kernel/locking/lockdep.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ecd92969674c..92bdb187987f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4147,10 +4147,8 @@ static void zap_class(struct lock_class *class)
 	 * Unhash the class and remove it from the all_lock_classes list:
 	 */
 	hlist_del_rcu(&class->hash_entry);
+	class->hash_entry.pprev = NULL;
 	list_del(&class->lock_entry);
-
-	RCU_INIT_POINTER(class->key, NULL);
-	RCU_INIT_POINTER(class->name, NULL);
 }
 
 static inline int within(const void *addr, void *start, unsigned long size)
-- 
2.20.0.rc1.387.gf8505762e3-goog