re: bin/57476: dhcpd dumps core

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR bin/57476; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, martin%NetBSD.org@localhost
Subject: re: bin/57476: dhcpd dumps core
Date: Thu, 22 Jun 2023 06:17:27 +1000

 >  From your debug info it looks as if in this loop:
 >  
 >  	for (bptr = hash [hashix]; bptr; bptr = bptr -> cdr) {
 >  		if (((struct option_cache *)(bptr -> car)) -> option -> code ==
 >  		    code)
 >  			return (struct option_cache *)(bptr -> car);
 >  	}
 >  
 >  bptr->car == 0   (NULL).   I can't tell on which iteration,
 
 when i first saw this PR, it made me ponder, but having you
 debug this far i'm convinced i have seen this problem on big
 endian arm64 the last year and a half (ever since switching
 my host over from a sparc64.)
 
 IIRC, this system went live in late feb last year, and i've
 seen this crash twice so far, so it does not happen often,
 and i did not see any obvious errors in the code here, but
 i suspect you looked further going on the next message.  my
 last crash was april, and i haven't seen the log trigger.
  
 i still have the latest core file lying around, but the
 binary is newer since i'm running with this patch now:
 
 
 Index: common/options.c
 ===================================================================
 RCS file: /cvsroot/src/external/mpl/dhcp/dist/common/options.c,v
 retrieving revision 1.5
 diff -p -r1.5 options.c
 *** common/options.c	13 Jan 2021 17:01:31 -0000	1.5
 --- common/options.c	21 Jun 2023 20:12:29 -0000
 *************** struct option_cache *lookup_hashed_optio
 *** 2497,2502 ****
 --- 2497,2507 ----
   
   	hashix = compute_option_hash (code);
   	for (bptr = hash [hashix]; bptr; bptr = bptr -> cdr) {
 + 		if (bptr -> car == NULL) {
 + 			log_error ("Null pointer in bptr -> cdr: %s(%d)",
 + 			   __func__, __LINE__);
 + 			continue;
 + 		}
   		if (((struct option_cache *)(bptr -> car)) -> option -> code ==
   		    code)
   			return (struct option_cache *)(bptr -> car);