[JENA-2172] WantPropertyElement.rdf_n() is not thread-safe

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Jena 2.7.4, Jena 4.2.0
• Fix Version/s: Jena 4.3.0
• Component/s: RDF/XML
• Assignee: Andy Seaborne
• Reporter: ian green
• Created: 27/Sep/21 07:13
• Updated: 09/Dec/21 10:21
• Resolved: 30/Sep/21 18:02

Description

In 2.7.4, concurrent calls to Model.read (on RDF/XML) are occasionally corrupting internal parser state which results in NPE.  This corruption is sticky - all subsequent RDF/XML parsing (at least via Model.read) is potentially affected.

com.hp.hpl.jena.rdf.arp.states.WantPropertyElement._rdf_n can be left with null elements when multiple threads race to expand the array.  One consequence of such null elements is that WantPropertyElement.predicate can be null, causing a NullPointerException when toObject() is called.

This was discovered in 2.7.4, but the same code is present in org.apache.jena.rdfxml.xmlinput.states.WantPropertyElement.  (I don't know the role that code plays in the latest Jena versions, so this issue may not be manifest in main.)

Issue Links

• links to: GitHub Pull Request #1079