[PATCH tip/core/rcu 10/13] security: apply lockdep-based checking to rcu_dereference() uses

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

Apply lockdep-ified RCU primitives to key_gc_keyring() and
keyring_destroy().

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 security/keys/gc.c      |    3 ++-
 security/keys/keyring.c |    4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/security/keys/gc.c b/security/keys/gc.c
index 4770be3..1990231 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -77,7 +77,8 @@ static bool key_gc_keyring(struct key *keyring, time_t limit)
 		goto dont_gc;
 
 	/* scan the keyring looking for dead keys */
-	klist = rcu_dereference(keyring->payload.subscriptions);
+	klist = rcu_dereference_check(keyring->payload.subscriptions,
+				      lockdep_is_held(&key_serial_lock));
 	if (!klist)
 		goto dont_gc;
 
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 8ec0274..e814d21 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -151,7 +151,9 @@ static void keyring_destroy(struct key *keyring)
 		write_unlock(&keyring_name_lock);
 	}
 
-	klist = rcu_dereference(keyring->payload.subscriptions);
+	klist = rcu_dereference_check(keyring->payload.subscriptions,
+				      rcu_read_lock_held() ||
+				      atomic_read(&keyring->usage) == 0);
 	if (klist) {
 		for (loop = klist->nkeys - 1; loop >= 0; loop--)
 			key_put(klist->keys[loop]);
-- 
1.6.6