push-notification: Switch to main ioloop while calling drivers' commi…

…t callbacks

There aren't any guarantees what ioloop happens to be active at the time
the commit is called. The active ioloop can also be destroyed early on,
which can cause an I/O leak and crashes later on.

src/plugins/push-notification/push-notification-plugin.c

@@ -2,6 +2,7 @@
 
 #include "lib.h"
 #include "array.h"
+#include "ioloop.h"
 #include "mail-namespace.h"
 #include "mail-storage.h"
 #include "mail-storage-private.h"
@@ -24,7 +25,7 @@
         MODULE_CONTEXT(obj, push_notification_user_module)
 static MODULE_CONTEXT_DEFINE_INIT(push_notification_user_module,
                                   &mail_user_module_register);
-
+static struct ioloop *main_ioloop;
 
 static void
 push_notification_transaction_init(struct push_notification_txn *ptxn)
@@ -102,14 +103,20 @@ static void push_notification_transaction_commit
 (void *txn, struct mail_transaction_commit_changes *changes)
 {
     struct push_notification_txn *ptxn = (struct push_notification_txn *)txn;
+    struct ioloop *prev_ioloop = current_ioloop;
 
+    /* Make sure we're not in just any random ioloop, which could get
+       destroyed soon. This way the push-notification drivers can do async
+       operations that finish in the main ioloop. */
+    io_loop_set_current(main_ioloop);
     if (changes == NULL) {
         push_notification_txn_mbox_end(ptxn);
     } else {
         push_notification_txn_msg_end(ptxn, changes);
     }
 
     push_notification_transaction_end(ptxn, TRUE);
+    io_loop_set_current(prev_ioloop);
 }
 
 static void push_notification_mailbox_create(struct mailbox *box)
@@ -337,6 +344,8 @@ void push_notification_plugin_init(struct module *module)
     push_notification_driver_register(&push_notification_driver_ox);
 
     push_notification_event_register_rfc5423_events();
+    main_ioloop = current_ioloop;
+    i_assert(main_ioloop != NULL);
 }
 
 void push_notification_plugin_deinit(void)