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/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 5ce31402..d1d17005 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/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;
       }

From 6e3449594fb2f61c92fc561f51f82196fdd15d63 Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Wed, 26 Jan 2022 02:51:39 +0100
Subject: [PATCH 2/2] Changes: Document CVE-2022-23990

---
 expat/Changes | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/expat/Changes b/expat/Changes
index 5ff5da5e..ec1f7604 100644
--- a/expat/Changes
+++ b/expat/Changes
@@ -10,12 +10,18 @@ Release x.x.x xxx xxxxxxx xx xxxx
                     for when XML_CONTEXT_BYTES is defined to >0 (which is both
                     common and default).
                     Impact is denial of service or more.
+            #551  CVE-2022-23990 -- Fix unsigned integer overflow in function
+                    doProlog triggered by large content in element type
+                    declarations when there is an element declaration handler
+                    present (from a prior call to XML_SetElementDeclHandler).
+                    Impact is denial of service or more.
 
         Bug fixes:
        #544 #545  xmlwf: Fix a memory leak on output file opening error
 
         Special thanks to:
             hwt0415
+            Roland Illig
             Samanta Navarro
                  and
             Clang LeakSan and the Clang team