From 85ae9a2d7d0e9358f356b33977b842df8ebaec2b Mon Sep 17 00:00:00 2001

From: Sebastian Pipping <sebastian@pipping.org>

Date: Sat, 25 Dec 2021 20:52:08 +0100

Subject: [PATCH] lib: Prevent integer overflow on m_groupSize in function

 doProlog (CVE-2021-46143)

---

 expat/lib/xmlparse.c | 15 +++++++++++++++

 1 file changed, 15 insertions(+)

diff --git a/lib/xmlparse.c b/lib/xmlparse.c

index b47c31b0..8f243126 100644

--- a/lib/xmlparse.c

+++ b/lib/xmlparse.c

@@ -5046,6 +5046,11 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,

       if (parser->m_prologState.level >= parser->m_groupSize) {

         if (parser->m_groupSize) {

           {

+            /* Detect and prevent integer overflow */

+            if (parser->m_groupSize > (unsigned int)(-1) / 2u) {

+              return XML_ERROR_NO_MEMORY;

+            }

+

             char *const new_connector = (char *)REALLOC(

                 parser, parser->m_groupConnector, parser->m_groupSize *= 2);

             if (new_connector == NULL) {

@@ -5056,6 +5061,16 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,

           }

           if (dtd->scaffIndex) {

+            /* Detect and prevent integer overflow.

+             * The preprocessor guard addresses the "always false" warning

+             * from -Wtype-limits on platforms where

+             * sizeof(unsigned int) < sizeof(size_t), e.g. on x86_64. */

+#if UINT_MAX >= SIZE_MAX

+            if (parser->m_groupSize > (size_t)(-1) / sizeof(int)) {

+              return XML_ERROR_NO_MEMORY;

+            }

+#endif

+

             int *const new_scaff_index = (int *)REALLOC(

                 parser, dtd->scaffIndex, parser->m_groupSize * sizeof(int));

             if (new_scaff_index == NULL)