Subject: Re: problems untarring 20020526-1.6A
To: None <,>
From: Tim Goodwin <>
List: netbsd-bugs
Date: 06/27/2002 15:21:50
> did anyone take a look on what's actually causing this problem? (is it
> nbpax? if yes, why?  do someone know how to fix it and eventuelly upload
> a new working snapshot?)

Yes, I've just found the bug in `pax -M'.

This is not sparc64 specific, but it does involve heap corruption, so
there's a good chance it won't show up on a different architecture.

1. The problem: buf_subs.c::bufpt is being corrupted; this results in
   pax failing to write a complete header, and the broken releases
   that we've all seen.

2. The cause: bufpt is being corrupted by code around line 550 of
   ftree.c (which is all inside a giant `if (Mflag)'; the problem only
   arises with `pax -M').  When fed with this input:

        . type=dir optional
        ./netbsd type=file

   the following code sets curdirlen to -1 (it is initially 1 for ".",
   but at this point ftnode->name is also ".").  Assigning to
   curdir[-1] stomps on bufpt.

   549                      if (ftnode != NULL) {
   550                              curdirlen -= strlen(ftnode->name) + 1;
   551                              curdir[curdirlen] = '\0';
   552                      }

3. The fix: I don't understand the code 100%, but the bug seems to be
   that curdir should be updated based on the old ftnode->name (we've
   just finished dealing with this one, so need to strip its name out
   of curdir); the current, buggy code updates ftnode first, then
   updates curdir using the new ftnode.  The appended patch changes
   the order of these.  In trivial testing it works (warning: I
   haven't done extensive testing).  At the very least, it should be
   sufficient to make working releases!


Index: ftree.c
RCS file: /cvsroot/basesrc/bin/pax/ftree.c,v
retrieving revision 1.20
diff -u -r1.20 ftree.c
--- ftree.c	20 Apr 2002 23:36:48 -0000	1.20
+++ ftree.c	27 Jun 2002 15:11:25 -0000
@@ -544,11 +544,10 @@
 				if (ftnode->parent == ftnode)
 					ftnode = NULL;
-				else
-					ftnode = ftnode->parent;
-				if (ftnode != NULL) {
+				else {
 					curdirlen -= strlen(ftnode->name) + 1;
 					curdir[curdirlen] = '\0';
+					ftnode = ftnode->parent;
 		} while (ftnode != NULL && ftnode->flags & F_VISIT);