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From: gww@marduk.UUCP (Gary Winiger)
Newsgroups: comp.bugs.4bsd
Subject: lpc help command dereferences a null pointer. +Fix
Message-ID: <519@elxsi.UUCP>
Date: Fri, 4-Sep-87 18:13:28 EDT
Article-I.D.: elxsi.519
Posted: Fri Sep  4 18:13:28 1987
Date-Received: Sat, 5-Sep-87 21:26:18 EDT
Sender: nobody@elxsi.UUCP
Reply-To: gww@marduk.UUCP (Gary Winiger)
Organization: ELXSI Super Computers, San Jose
Lines: 66


Subject: The lpc help command dereferences a null pointer. +Fix
Index:	usr.lib/lpr/lpc.c 4.3BSD +Fix

Description:
	When printing help from lpc the null pointer at the end of the
	command table is dereferenced.
Repeat-By:
	Bring up lpc, type ? and watch it core dump on a system which
	does not permit null pointer dereferencing.
Fix:
	NCMDS is the number of commands in the cmdtab, including the 
	null command that ends the table.
	In the help command, stop printing at NCMDS-1.
	The attached code solves this problem at Elxsi.

Gary..
{ucbvax!sun,lll-lcc!lll-tis,amdahl!altos86,bridge2}!elxsi!gww
--------- cut --------- snip --------- :.,$w diff -------------
*** /tmp/,RCSt1013466	Mon Jun 22 17:24:00 1987
--- lpc.c	Mon Jun 22 17:23:36 1987
***************
*** 1,5 ****
--- 1,8 ----
  /*
   * $Log:	lpc.c,v $
+  * Revision 1.2  87/06/22  17:23:10  gww
+  * Don't dereference the null pointer at the end of the command table.
+  * 
   * Revision 1.1  87/06/16  16:25:39  gww
   * Initial revision
   * 
***************
*** 17,23 ****
  #endif not lint
  
  #ifndef lint
! static char *ERcsId = "$Header: lpc.c,v 1.1 87/06/16 16:25:39 gww Exp $ ENIX BSD";
  static char sccsid[] = "@(#)lpc.c	5.2 (Berkeley) 11/17/85";
  #endif not lint
  
--- 20,26 ----
  #endif not lint
  
  #ifndef lint
! static char *ERcsId = "$Header: lpc.c,v 1.2 87/06/22 17:23:10 gww Exp $ ENIX BSD";
  static char sccsid[] = "@(#)lpc.c	5.2 (Berkeley) 11/17/85";
  #endif not lint
  
***************
*** 197,203 ****
  		extern int NCMDS;
  
  		printf("Commands may be abbreviated.  Commands are:\n\n");
! 		for (c = cmdtab; c < &cmdtab[NCMDS]; c++) {
  			int len = strlen(c->c_name);
  
  			if (len > width)
--- 200,206 ----
  		extern int NCMDS;
  
  		printf("Commands may be abbreviated.  Commands are:\n\n");
! 		for (c = cmdtab; c < &cmdtab[NCMDS-1]; c++) {
  			int len = strlen(c->c_name);
  
  			if (len > width)