Propagate enlargeStringInfo() fixes into the equivalent code in

pqexpbuffer.c.  While a client-side failure doesn't seem like a
security issue, it's still a bug.

Author: tglsfdc

src/interfaces/libpq/pqexpbuffer.c

@@ -17,13 +17,15 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.16 2003/11/29 19:52:12 pgsql Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.17 2004/05/14 00:20:38 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 
 #include "postgres_fe.h"
 
+#include <limits.h>
+
 #include "pqexpbuffer.h"
 
 #ifdef WIN32
@@ -132,7 +134,18 @@ enlargePQExpBuffer(PQExpBuffer str, size_t needed)
 	size_t		newlen;
 	char	   *newdata;
 
+	/*
+	 * Guard against ridiculous "needed" values, which can occur if we're
+	 * fed bogus data.  Without this, we can get an overflow or infinite
+	 * loop in the following.
+	 */
+	if (needed >= ((size_t) INT_MAX - str->len))
+		return 0;
+
 	needed += str->len + 1;		/* total space required now */
+
+	/* Because of the above test, we now have needed <= INT_MAX */
+
 	if (needed <= str->maxlen)
 		return 1;				/* got enough space already */
 
@@ -146,6 +159,14 @@ enlargePQExpBuffer(PQExpBuffer str, size_t needed)
 	while (needed > newlen)
 		newlen = 2 * newlen;
 
+	/*
+	 * Clamp to INT_MAX in case we went past it.  Note we are assuming
+	 * here that INT_MAX <= UINT_MAX/2, else the above loop could
+	 * overflow.  We will still have newlen >= needed.
+	 */
+	if (newlen > (size_t) INT_MAX)
+		newlen = (size_t) INT_MAX;
+
 	newdata = (char *) realloc(str->data, newlen);
 	if (newdata != NULL)
 	{