[libsecret/wip/mcrha/flatpak-use-after-free-fix] secret-file-backend: Fix use-after-free in flatpak

[Milan Crha <mcrha src gnome org>]

commit 523fe32b65f1561352986f186f3cd0eb4698a8b3
Author: Milan Crha <mcrha redhat com>
Date:   Thu Mar 19 09:24:52 2020 +0100

    secret-file-backend: Fix use-after-free in flatpak
    
    The on_portal_retrieve_secret() can connect a GCancellable, but it
    doesn't disconnect from it (only when the cancellable is cancelled),
    which means when the cancellable is cancelled later, when the GTask
    is gone, the callback is called with already freed data.

 libsecret/secret-file-backend.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/libsecret/secret-file-backend.c b/libsecret/secret-file-backend.c
index e69c319..649ef0d 100644
--- a/libsecret/secret-file-backend.c
+++ b/libsecret/secret-file-backend.c
@@ -231,6 +231,11 @@ on_portal_response (GDBusConnection *connection,
        InitClosure *init = g_task_get_task_data (task);
        guint32 response;
 
+       if (init->cancellable_signal_id) {
+               g_cancellable_disconnect (g_task_get_cancellable (task), init->cancellable_signal_id);
+               init->cancellable_signal_id = 0;
+       }
+
        g_dbus_connection_signal_unsubscribe (connection,
                                              init->portal_signal_id);
 
@@ -303,6 +308,7 @@ on_portal_cancel (GCancellable *cancellable,
                                task);
 
        g_cancellable_disconnect (cancellable, init->cancellable_signal_id);
+       init->cancellable_signal_id = 0;
 }
 
 static void