From ede41d1e186ed2aba88a06e84cac839b770af3a1 Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Wed, 26 Jan 2022 02:36:43 +0100
Subject: [PATCH 1/2] lib: Prevent integer overflow in doProlog
 (CVE-2022-23990)

The change from "int nameLen" to "size_t nameLen"
addresses the overflow on "nameLen++" in code
"for (; name[nameLen++];)" right above the second
change in the patch.
---
 expat/lib/xmlparse.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/xmlparse.c b/lib/xmlparse.c
index 5ce31402..d1d17005 100644
--- a/lib/xmlparse.c
+++ b/lib/xmlparse.c
@@ -5372,7 +5372,7 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,
       if (dtd->in_eldecl) {
         ELEMENT_TYPE *el;
         const XML_Char *name;
-        int nameLen;
+        size_t nameLen;
         const char *nxt
             = (quant == XML_CQUANT_NONE ? next : next - enc->minBytesPerChar);
         int myindex = nextScaffoldPart(parser);
@@ -5388,7 +5388,13 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,
         nameLen = 0;
         for (; name[nameLen++];)
           ;
-        dtd->contentStringLen += nameLen;
+
+        /* Detect and prevent integer overflow */
+        if (nameLen > UINT_MAX - dtd->contentStringLen) {
+          return XML_ERROR_NO_MEMORY;
+        }
+
+        dtd->contentStringLen += (unsigned)nameLen;
         if (parser->m_elementDeclHandler)
           handleDefault = XML_FALSE;
       }