[PATCH v5 05/12] keys: add call key_put_sync() to flush key_gc_work when doing a key_put().

[Dave Jiang <dave.jiang@intel.com>]

Adding key_put_sync() that calls flush_work on key_gc_work to ensure the
key we want to remove is gone.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
 include/linux/key.h |    1 +
 security/keys/key.c |   35 +++++++++++++++++++++++++++++------
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/include/linux/key.h b/include/linux/key.h
index e58ee10f6e58..4dffbd23d4e4 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -253,6 +253,7 @@ extern struct key *key_alloc(struct key_type *type,
 extern void key_revoke(struct key *key);
 extern void key_invalidate(struct key *key);
 extern void key_put(struct key *key);
+extern void key_put_sync(struct key *key);
 
 static inline struct key *__key_get(struct key *key)
 {
diff --git a/security/keys/key.c b/security/keys/key.c
index d97c9394b5dd..b6f3ec19ab0f 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -622,6 +622,19 @@ int key_reject_and_link(struct key *key,
 }
 EXPORT_SYMBOL(key_reject_and_link);
 
+static void __key_put(struct key *key, bool sync)
+{
+	if (key) {
+		key_check(key);
+
+		if (refcount_dec_and_test(&key->usage)) {
+			schedule_work(&key_gc_work);
+			if (sync)
+				flush_work(&key_gc_work);
+		}
+	}
+}
+
 /**
  * key_put - Discard a reference to a key.
  * @key: The key to discard a reference from.
@@ -632,15 +645,25 @@ EXPORT_SYMBOL(key_reject_and_link);
  */
 void key_put(struct key *key)
 {
-	if (key) {
-		key_check(key);
-
-		if (refcount_dec_and_test(&key->usage))
-			schedule_work(&key_gc_work);
-	}
+	__key_put(key, false);
 }
 EXPORT_SYMBOL(key_put);
 
+/**
+ * key_put - Discard a reference to a key and flush the key gc work item.
+ * @key: The key to discard a reference from.
+ *
+ * Discard a reference to a key, and when all the references are gone, we
+ * schedule the cleanup task to come and pull it out of the tree in process
+ * context at some later time. This call flushes the clean up so we are sure
+ * that the key is gone.
+ */
+void key_put_sync(struct key *key)
+{
+	__key_put(key, true);
+}
+EXPORT_SYMBOL(key_put_sync);
+
 /*
  * Find a key by its serial number.
  */

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