linux-kernel - [PATCH v3 21/24] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

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Message-Id: <20181207011148.251812-22-bvanassche@acm.org>
Date:   Thu,  6 Dec 2018 17:11:45 -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 v3 21/24] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

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 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 8c69516b1283..a47357d3dca7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -727,6 +727,15 @@ static bool assign_lock_key(struct lockdep_map *lock)
 {
 	unsigned long can_addr, addr = (unsigned long)lock;
 
+	/*
+	 * lockdep_free_key_range() assumes that struct lock_class_key
+	 * objects do not overlap. Since we use the address of lock
+	 * objects as class key for static objects, check whether the
+	 * size of lock_class_key objects does not exceed the size of
+	 * the smallest lock object.
+	 */
+	BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
+
 	if (__is_kernel_percpu_address(addr, &can_addr))
 		lock->key = (void *)can_addr;
 	else if (__is_module_percpu_address(addr, &can_addr))
-- 
2.20.0.rc2.403.gdbc3b29805-goog