[BusyBox 0001429]: tar failed to unpack *.tar archive

bugs at busybox.net bugs at busybox.net
Tue Jul 17 08:26:04 UTC 2007


A NOTE has been added to this issue. 
====================================================================== 
http://busybox.net/bugs/view.php?id=1429 
====================================================================== 
Reported By:                vicser
Assigned To:                BusyBox
====================================================================== 
Project:                    BusyBox
Issue ID:                   1429
Category:                   Standards Compliance
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     assigned
====================================================================== 
Date Submitted:             07-16-2007 03:18 PDT
Last Modified:              07-17-2007 01:26 PDT
====================================================================== 
Summary:                    tar failed to unpack *.tar archive
Description: 
busybox 1.3.2 - 1.6.1
Kernel 2.4.30 (i386 PC)

tar failed to unpack archive
Error is in busybox 1.3.2 - 1.6.1
Last time tested on busybox 1.6.1 (build configuration is in attached
.config)

How to reproduce (see attachement mod_net.tar)
tar xf mod_net.tar

Operaton failes with the error message

	tar: short read

All archivers on desktop Linux systems unpack this file without errors

Archive is created by the win32 port of gnu tar:
	http://gnuwin32.sourceforge.net/
	http://gnuwin32.sourceforge.net/packages/tar.htm

Improtant thing is that not all archives created by gnuwin32 tar
are unpackable by busybox tar - some are unpacked without problems
====================================================================== 

---------------------------------------------------------------------- 
 vicser - 07-16-07 03:20  
---------------------------------------------------------------------- 
.config is Busybox 1.6.1 build configuration 

---------------------------------------------------------------------- 
 vicser - 07-16-07 03:23  
---------------------------------------------------------------------- 
tar.exe is tar from   http://gnuwin32.sourceforge.net
You ned additional libaries to launch it
See:
  http://gnuwin32.sourceforge.net/downlinks/tar-dep-zip.php 

---------------------------------------------------------------------- 
 vda - 07-16-07 14:14  
---------------------------------------------------------------------- 
GNU tar also complains:

# tar xvf mod_net.tar
tulip.o
tar: short read
# /usr/bin/tar xvf mod_net.tar
tulip.o
/usr/bin/tar: A lone zero block at 100
# /usr/bin/tar --version
tar (GNU tar) 1.15.1

If you will do

# hexdump -vC mod_net.tar >mod_net.tar.hex

you will see that the reason for the warning is that there is only one
512-byte zero block at the end (at 0000c600). There should be at least 2
such blocks to mark EOF.

Both busybox and GNU tar unpack the file ok, the only difference is that
GNU tar exits with "success" and bbox tar does not:

# /usr/bin/tar xvf mod_net.tar; echo $?
tulip.o
/usr/bin/tar: A lone zero block at 100
0
# tar xvf mod_net.tar; echo $?
tulip.o
tar: short read
1

Is this a problem for you? 

---------------------------------------------------------------------- 
 vicser - 07-17-07 01:26  
---------------------------------------------------------------------- 
Yes, really this is a problem, because it is impossible to check if
unpacking
succeeds without extra manipulations (as md5 check)

In any case thanks for explanation
I understand that this is a problem on packing side.

I don't insist on such behaviour but I think it would be
convenient if busybox tar would be able to handle such issue
(whereas usefull data in tar file are really correct) and return
SUCCESS error code and warning (like gnu tar) 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
07-16-07 03:18  vicser         New Issue                                    
07-16-07 03:18  vicser         Status                   new => assigned     
07-16-07 03:18  vicser         Assigned To               => BusyBox         
07-16-07 03:18  vicser         File Added: mod_net.tar                      
07-16-07 03:19  vicser         File Added: .config                          
07-16-07 03:20  vicser         Note Added: 0002605                          
07-16-07 03:21  vicser         File Added: tar.exe                          
07-16-07 03:23  vicser         Note Added: 0002606                          
07-16-07 05:43  vicser         Issue Monitored: vicser                      
07-16-07 05:43  vicser         Issue End Monitor: vicser                    
07-16-07 14:14  vda            Note Added: 0002607                          
07-17-07 01:26  vicser         Note Added: 0002608                          
======================================================================




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