IXR_Message XML parsing leaks memory in PHP 7.0.0 and above

[procifer]

IXR_Message uses the xml_parser_free function after it has parsed an XML RPC response. However, as of PHP 7.0.0, it's also necessary to explicitly unset the reference to the parser to avoid memory leaks:
​https://www.php.net/manual/en/function.xml-parser-free.php

I'm including a patch that adds an unset after the parser is freed, and also adds a xml_parser_free/unset pair before returning early when the parser fails.

I also see other uses of xml_parser_free in a quick search of the codebase, so might be good for someone with more knowledge than me to review those as well.

[ayeshrajans]

Hi @procifer - welcome to WordPress Trac. This indeed is a great find, and the patch looks good to me too.

[procifer]

Replying to ayeshrajans:

Hi @procifer - welcome to WordPress Trac. This indeed is a great find, and the patch looks good to me too.

Thank you so much @ayeshrajans !

[SergeyBiryukov]

In 48322:

XML-RPC: Explicitly unset the reference to the parser resource after calling xml_parser_free() to avoid memory leaks in PHP 7.0.0 or higher.

Props procifer, ayeshrajans.
Fixes #49700.