api: Upon bucket delete remove in-memory state properly. (#4716)

This PR fixes the issue of cleaning up in-memory state
properly. Without this PR we can lead to security
situations where new bucket would inherit wrong
permissions on bucket and expose objects erroneously.

Fixes #4714

cmd/bucket-handlers.go

@@ -653,12 +653,21 @@ func (api objectAPIHandlers) DeleteBucketHandler(w http.ResponseWriter, r *http.
 	// Delete bucket access policy, if present - ignore any errors.
 	_ = removeBucketPolicy(bucket, objectAPI)
 
+	// Notify all peers (including self) to update in-memory state
+	S3PeersUpdateBucketPolicy(bucket, policyChange{true, nil})
+
 	// Delete notification config, if present - ignore any errors.
 	_ = removeNotificationConfig(bucket, objectAPI)
 
+	// Notify all peers (including self) to update in-memory state
+	S3PeersUpdateBucketNotification(bucket, nil)
+
 	// Delete listener config, if present - ignore any errors.
 	_ = removeListenerConfig(bucket, objectAPI)
 
+	// Notify all peers (including self) to update in-memory state
+	S3PeersUpdateBucketListener(bucket, []listenerConfig{})
+
 	// Write success response.
 	writeSuccessNoContent(w)
 }

cmd/event-notifier.go

@@ -503,9 +503,8 @@ func removeNotificationConfig(bucket string, objAPI ObjectLayer) error {
 	// Acquire a write lock on notification config before modifying.
 	objLock := globalNSMutex.NewNSLock(minioMetaBucket, ncPath)
 	objLock.Lock()
-	err := objAPI.DeleteObject(minioMetaBucket, ncPath)
-	objLock.Unlock()
-	return err
+	defer objLock.Unlock()
+	return objAPI.DeleteObject(minioMetaBucket, ncPath)
 }
 
 // Remove listener configuration from storage layer. Used when a bucket is deleted.
@@ -516,9 +515,8 @@ func removeListenerConfig(bucket string, objAPI ObjectLayer) error {
 	// Acquire a write lock on notification config before modifying.
 	objLock := globalNSMutex.NewNSLock(minioMetaBucket, lcPath)
 	objLock.Lock()
-	err := objAPI.DeleteObject(minioMetaBucket, lcPath)
-	objLock.Unlock()
-	return err
+	defer objLock.Unlock()
+	return objAPI.DeleteObject(minioMetaBucket, lcPath)
 }
 
 // Loads both notification and listener config.