[QPID-8397] Memory leak in QueueBindings list

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: qpid-cpp-1.40.0
• Component/s: C++ Broker
• Assignee: Clifford Jansen
• Reporter: Clifford Jansen
• Created: 06/Jan/20 07:20
• Updated: 06/Jan/20 07:40

Description

The Queue remembers the bindings it belongs to in its QueueBindings class. There is an add() but no corresponding remove() method. If repeated bind and unbind operations are done in succession (between the same exchange-queue pair), duplicates pile up in the QueueBindings but not in the exchange binding list.

The remembered QueueBindings are only ever actively used in two cases: a simple unit_test case and on deletion of the Queue to free its resources, including bindings. Neither case suffers from working with duplicates, aside from the memory waste while the queue is alive. Memory is reclaimed when the queue is destroyed, so valgrind is happy.

However, some usage patterns can allow many duplicates to accumulate. See

https://bugzilla.redhat.com/show_bug.cgi?id=1778703

There is more than one mechanism used within the broker to create a binding:

Exchange::bind() + Queue::bound()

Queue::bind() which essentially does the former

To fix this leak without a refactor, both forms needs to be located in the code and symmetric "unbind" operations need to deallocate the QueueBindings reference.