[IMPALA-10942] Fix memory leak in admission controller

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Impala 4.0.0
• Fix Version/s: Impala 4.1.0
• Component/s: Backend
• Labels: memory-leak
• Epic Color: ghx-label-12
• Assignee: Bikramjeet Vig
• Reporter: Bikramjeet Vig
• Created: 30/Sep/21 20:07
• Updated: 19/Jul/23 17:23
• Resolved: 05/Apr/22 17:55

Description

https://github.com/apache/impala/blob/1a61a8025c87c37921a1bba4c49f754d8bd10bcc/be/src/scheduling/admission-controller.cc#L1196

The intent of the aforementioned line in the code was to check and remove the queue_node if the query was not queued. Instead it end up checking whether that flag is a null pointer or not. Since a valid pointer is always sent, this would result in the queue node never being removed resulting in a memory leak