From 1cee06ac02b0f12ba748c341a41cfd7fd1fb5ea9 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 21 Aug 2007 02:40:06 +0000
Subject: [PATCH] Fix potential access-off-the-end-of-memory in varbit_out():
 it fetched the byte after the last full byte of the bit array, regardless of
 whether that byte was part of the valid data or not.  Found by buildfarm
 testing. Thanks to Stefan Kaltenbrunner for nailing down the cause.

---
 src/backend/utils/adt/varbit.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index 3126bd689c..b6ab6bb1e7 100644
--- a/src/backend/utils/adt/varbit.c
+++ b/src/backend/utils/adt/varbit.c
@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/varbit.c,v 1.54 2007/06/15 20:56:51 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/varbit.c,v 1.55 2007/08/21 02:40:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -537,8 +537,9 @@ varbit_out(PG_FUNCTION_ARGS)
 	result = (char *) palloc(len + 1);
 	sp = VARBITS(s);
 	r = result;
-	for (i = 0; i < len - BITS_PER_BYTE; i += BITS_PER_BYTE, sp++)
+	for (i = 0; i <= len - BITS_PER_BYTE; i += BITS_PER_BYTE, sp++)
 	{
+		/* print full bytes */
 		x = *sp;
 		for (k = 0; k < BITS_PER_BYTE; k++)
 		{
@@ -546,11 +547,15 @@ varbit_out(PG_FUNCTION_ARGS)
 			x <<= 1;
 		}
 	}
-	x = *sp;
-	for (k = i; k < len; k++)
+	if (i < len)
 	{
-		*r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
-		x <<= 1;
+		/* print the last partial byte */
+		x = *sp;
+		for (k = i; k < len; k++)
+		{
+			*r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
+			x <<= 1;
+		}
 	}
 	*r = '\0';
 
-- 
2.40.0