[PATCH v7 04/23] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache

[Bart Van Assche]

Make sure that add_chain_cache() returns 0 and does not modify the
chain hash if nr_chain_hlocks == MAX_LOCKDEP_CHAIN_HLOCKS before this
function is called.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 kernel/locking/lockdep.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b00c6edd6a28..404086b23fc7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2206,16 +2206,8 @@ static inline int add_chain_cache(struct task_struct *curr,
 			chain_hlocks[chain->base + j] = lock_id;
 		}
 		chain_hlocks[chain->base + j] = class - lock_classes;
-	}
-
-	if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
 		nr_chain_hlocks += chain->depth;
-
-#ifdef CONFIG_DEBUG_LOCKDEP
-	/*
-	 * Important for check_no_collision().
-	 */
-	if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
+	} else {
 		if (!debug_locks_off_graph_unlock())
 			return 0;
 
@@ -2223,7 +2215,6 @@ static inline int add_chain_cache(struct task_struct *curr,
 		dump_stack();
 		return 0;
 	}
-#endif
 
 	hlist_add_head_rcu(&chain->entry, hash_head);
 	debug_atomic_inc(chain_lookup_misses);
-- 
2.21.0.rc0.258.g878e2cd30e-goog