io: fix cleanup for TLS I/O source data on cancellation

The TLS code will create a GSource for tracking completion of the
handshake process, passing a QIOChannelTLSData struct that contains
various data items. The data struct is freed by the callback when
it completes, which means when a source is cancelled, nothing is
free'ing the data struct or its contents.

Switch to provide a data free callback to the GSource, which ensures
the QIOChannelTLSData struct is always freed even when the main event
callback never fires.

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/3114
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

io/channel-tls.c

@@ -153,13 +153,32 @@ struct QIOChannelTLSData {
 };
 typedef struct QIOChannelTLSData QIOChannelTLSData;
 
+static void qio_channel_tls_io_data_free(gpointer user_data)
+{
+    QIOChannelTLSData *data = user_data;
+    /*
+     * Usually 'task' will be NULL since the GSource
+     * callback will either complete the task or pass
+     * it on to a new GSource. We'll see a non-NULL
+     * task here only if the GSource was released before
+     * its callback triggers
+     */
+    if (data->task) {
+        qio_task_free(data->task);
+    }
+    if (data->context) {
+        g_main_context_unref(data->context);
+    }
+    g_free(data);
+}
+
 static gboolean qio_channel_tls_handshake_io(QIOChannel *ioc,
                                              GIOCondition condition,
                                              gpointer user_data);
 
-static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
-                                           QIOTask *task,
-                                           GMainContext *context)
+static gboolean qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
+                                               QIOTask *task,
+                                               GMainContext *context)
 {
     Error *err = NULL;
     int status;
@@ -170,8 +189,7 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
         trace_qio_channel_tls_handshake_fail(ioc);
         qio_task_set_error(task, err);
         qio_task_complete(task);
-        qio_task_free(task);
-        return;
+        return TRUE;
     }
 
     if (status == QCRYPTO_TLS_HANDSHAKE_COMPLETE) {
@@ -184,7 +202,7 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
             trace_qio_channel_tls_credentials_allow(ioc);
         }
         qio_task_complete(task);
-        qio_task_free(task);
+        return TRUE;
     } else {
         GIOCondition condition;
         QIOChannelTLSData *data = g_new0(typeof(*data), 1);
@@ -208,8 +226,9 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
                                        condition,
                                        qio_channel_tls_handshake_io,
                                        data,
-                                       NULL,
+                                       qio_channel_tls_io_data_free,
                                        context);
+        return FALSE;
     }
 }
 
@@ -225,11 +244,9 @@ static gboolean qio_channel_tls_handshake_io(QIOChannel *ioc,
         qio_task_get_source(task));
 
     tioc->hs_ioc_tag = 0;
-    g_free(data);
-    qio_channel_tls_handshake_task(tioc, task, context);
-
-    if (context) {
-        g_main_context_unref(context);
+    if (!qio_channel_tls_handshake_task(tioc, task, context)) {
+        /* task is kept by new GSource so must not be released yet */
+        data->task = NULL;
     }
 
     return FALSE;
@@ -252,14 +269,16 @@ void qio_channel_tls_handshake(QIOChannelTLS *ioc,
                         func, opaque, destroy);
 
     trace_qio_channel_tls_handshake_start(ioc);
-    qio_channel_tls_handshake_task(ioc, task, context);
+    if (qio_channel_tls_handshake_task(ioc, task, context)) {
+        qio_task_free(task);
+    }
 }
 
 static gboolean qio_channel_tls_bye_io(QIOChannel *ioc, GIOCondition condition,
                                        gpointer user_data);
 
-static void qio_channel_tls_bye_task(QIOChannelTLS *ioc, QIOTask *task,
-                                     GMainContext *context)
+static gboolean qio_channel_tls_bye_task(QIOChannelTLS *ioc, QIOTask *task,
+                                         GMainContext *context)
 {
     GIOCondition condition;
     QIOChannelTLSData *data;
@@ -272,14 +291,12 @@ static void qio_channel_tls_bye_task(QIOChannelTLS *ioc, QIOTask *task,
         trace_qio_channel_tls_bye_fail(ioc);
         qio_task_set_error(task, err);
         qio_task_complete(task);
-        qio_task_free(task);
-        return;
+        return TRUE;
     }
 
     if (status == QCRYPTO_TLS_BYE_COMPLETE) {
         qio_task_complete(task);
-        qio_task_free(task);
-        return;
+        return TRUE;
     }
 
     data = g_new0(typeof(*data), 1);
@@ -299,7 +316,10 @@ static void qio_channel_tls_bye_task(QIOChannelTLS *ioc, QIOTask *task,
     trace_qio_channel_tls_bye_pending(ioc, status);
     ioc->bye_ioc_tag = qio_channel_add_watch_full(ioc->master, condition,
                                                   qio_channel_tls_bye_io,
-                                                  data, NULL, context);
+                                                  data,
+                                                  qio_channel_tls_io_data_free,
+                                                  context);
+    return FALSE;
 }
 
 
@@ -312,11 +332,9 @@ static gboolean qio_channel_tls_bye_io(QIOChannel *ioc, GIOCondition condition,
     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(qio_task_get_source(task));
 
     tioc->bye_ioc_tag = 0;
-    g_free(data);
-    qio_channel_tls_bye_task(tioc, task, context);
-
-    if (context) {
-        g_main_context_unref(context);
+    if (!qio_channel_tls_bye_task(tioc, task, context)) {
+        /* task is kept by new GSource so must not be released yet */
+        data->task = NULL;
     }
 
     return FALSE;