Dbm library

[Gary Winiger]

In article <580 at xyzzy.UUCP> meissner at .UUCP (Michael Meissner) writes:
> I remember quite awhile ago, there was a discussion of problems in the
> dbm library, particularly when it has to split an index node.

Some time last September, I filed the following bug report and fix.  Here
it is again for all those who need it.  The UCB VAX C compiler does not
have this problem, because it doesn't treat sizeof as an unsigned.

Gary..
{uunet,sun,lll-tis}!elxsi!gww

Subject: dbm_store fails on first attempt to write .pag file. +Fix
Index:	libc/gen/ndbm.c 4.3BSD +Fix

Description:
	dbm_store fails when the first .pag write is done.
Repeat-By:
	mkpasswd passwd
Fix:
	The comparison for .pag buffer overflow in additem fails to
	recognize overflow.  This is due to the size_t (of sizeof) being
	unsigned, thus promoting the comparison to unsigned.  The C 
	standard, in C.3.3.4, states:
	``... and its type (an unsigned integral type) is size_t.''
	Casting sizeof to int resolves this problem at ELXSI.

Gary..
{ucbvax!sun,lll-lcc!lll-tis,amdahl!altos86,bridge2}!elxsi!gww
--------- cut --------- snip --------- :.,$w diff -------------
*** /tmp/,RCSt1000709	Fri Mar 27 17:12:31 1987
--- ndbm.c	Fri Mar 27 17:12:12 1987
***************
*** 1,5 ****
--- 1,10 ----
  /*
   * $Log:	ndbm.c,v $
+  * Revision 1.2  87/03/27  17:08:45  gww
+  * Cast sizeof to int.  This comparison will fail when i1 is < 0 because the
+  * type of sizeof (according to C standard C.3.3.4) is unsigned thus causing
+  * the comparison to fail because it is promoted to unsigned.
+  * 
   * Revision 1.1  87/01/15  15:35:33  gww
   * Initial revision
   * 
***************
*** 11,17 ****
   */
  
  #if defined(LIBC_SCCS) && !defined(lint)
! static char *ERcsId = "$Header: ndbm.c,v 1.1 87/01/15 15:35:33 gww Exp $ ENIX BSD";
  static char sccsid[] = "@(#)ndbm.c	5.3 (Berkeley) 3/9/86";
  #endif LIBC_SCCS and not lint
  
--- 16,22 ----
   */
  
  #if defined(LIBC_SCCS) && !defined(lint)
! static char *ERcsId = "$Header: ndbm.c,v 1.2 87/03/27 17:08:45 gww Exp $ ENIX BSD";
  static char sccsid[] = "@(#)ndbm.c	5.3 (Berkeley) 3/9/86";
  #endif LIBC_SCCS and not lint
  
***************
*** 503,509 ****
  	if (i2 > 0)
  		i1 = sp[i2];
  	i1 -= item.dsize + item1.dsize;
! 	if (i1 <= (i2+3) * sizeof(short))
  		return (0);
  	sp[0] += 2;
  	sp[++i2] = i1 + item1.dsize;
--- 508,514 ----
  	if (i2 > 0)
  		i1 = sp[i2];
  	i1 -= item.dsize + item1.dsize;
! 	if (i1 <= (i2+3) * (int)sizeof(short))
  		return (0);
  	sp[0] += 2;
  	sp[++i2] = i1 + item1.dsize;