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.

diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index 00527c45f18a378b9b1911a2af0761daad97282c..0143e0aa9c6eab4cca8f25314b4f6a094edf22c4 100644 (file)
--- 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
- *       $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.37 2003/09/25 06:58:05 petere Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.37.2.1 2007/08/21 02:40:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -430,8 +430,9 @@ 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++)
                {
@@ -439,11 +440,15 @@ varbit_out(PG_FUNCTION_ARGS)
                        x <<= 1;
                }
        }
-       x = *sp;
-       for (k = i; k < len; k++)
+       if (i < len)
        {
-               *r++ = (x & BITHIGH) ? '1' : '0';
-               x <<= 1;
+               /* print the last partial byte */
+               x = *sp;
+               for (k = i; k < len; k++)
+               {
+                       *r++ = (x & BITHIGH) ? '1' : '0';
+                       x <<= 1;
+               }
        }
        *r = '\0';