From d17619344dda05f9bc9b3f98a0c82f2f68939605 Mon Sep 17 00:00:00 2001 From: Kim Alvefur Date: Thu, 20 Jan 2022 09:57:20 +0100 Subject: util.xml: Break reference to help the GC (fix #1711) LuaExpat uses a registry reference to track handlers, which makes it so that an upvalue like this creates a reference loop that keeps the parser and its handlers from being garbage collected. The same issue has affected util.xmppstream in the past. Code for checking: local xml_parse = require"util.xml".parse; for i = 1, 10000 do xml_parse("") end collectgarbage(); collectgarbage(); print(collectgarbage("count"), "KiB"); A future release of LuaExpat may fix the underlying issue there. --- util/xml.lua | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/util/xml.lua b/util/xml.lua index 700da1d4..72f1a26b 100644 --- a/util/xml.lua +++ b/util/xml.lua @@ -65,27 +65,26 @@ local parse_xml = (function() function handler:EndElement() stanza:up(); end - local parser; -- SECURITY: These two handlers, especially the Doctype one, are required to prevent exploits such as Billion Laughs. function handler:StartDoctypeDecl() - if not parser.stop or not parser:stop() then + if not self.stop or not self:stop() then error("Failed to abort parsing"); end end function handler:ProcessingInstruction() - if not parser.stop or not parser:stop() then + if not self.stop or not self:stop() then error("Failed to abort parsing"); end end if not options or not options.allow_comments then -- NOTE: comments are generally harmless and can be useful when parsing configuration files or other data, even user-provided data function handler:Comment() - if not parser.stop or not parser:stop() then + if not self.stop or not self:stop() then error("Failed to abort parsing"); end end end - parser = lxp.new(handler, ns_separator); + local parser = lxp.new(handler, ns_separator); local ok, err, line, col = parser:parse(xml); if ok then ok, err, line, col = parser:parse(); end --parser:close(); -- cgit v1.2.3