Debian bug report logs - #1358
tar can't extract device numbers stored using cpio -Hustar

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Date: Thu, 14 Sep 95 19:51 BST
From: Ian Jackson <iwj10@cus.cam.ac.uk>
To: Debian bugs submission address <debian-bugs@pixar.com>
X-Debian-Cc: Nick Maclaren <nmm1@cus.cam.ac.uk>
Subject: tar can't extract device numbers stored using cpio -Hustar
Precedence: air-mail

Package: tar
Version: 1.11.8-1

chiark:~/junk> cd /dev
chiark:/dev> echo null | cpio -Hustar -O/u/ian/junk/t -vo
null
3 blocks
chiark:/dev> tar vvtf ~/junk/t
tar: Blocksize = 3 records
crw-rw-rw- 0/3             0,0 Mar 30 21:18 1995 null
chiark:/dev> cd ~/junk/
chiark:~/junk> really tar vvxf t 
tar: Blocksize = 3 records
crw-rw-rw- 0/3             0,0 Mar 30 21:18 1995 null
chiark:~/junk> ll null 
crw-rw-r--   1 root     sys        0,   0 Mar 30 21:18 null
chiark:~/junk> ll /dev/null 
crw-rw-rw-   1 root     sys        1,   3 Mar 30 21:18 /dev/null
chiark:~/junk> cpio -tv -Ft
crw-rw-rw-   1 root     sys        1,   3 Mar 30 21:18 null
2 blocks
chiark:~/junk> rm null 
rm: remove `null', overriding mode 0664? y
chiark:~/junk> really cpio -iv -Ft
null
2 blocks
chiark:~/junk> ll null 
crw-rw-rw-   1 root     sys        1,   3 Sep 14 19:38 null
chiark:~/junk> gzip -9v <t | uuencode t.gz
 94.6%
begin 664 t.gz
M'XL(`!]V6#`"`\LKS<EAH#%0,#(P,S-38%```0,H;0REH6*FYL9F9H:&!F:&
M0'%#`Q-S<P4&8P8Z@-+BDL0B!@.#HOS\$GSJBBN+\7L2!`P1GAL%HV`4C()!
*#@#(#'K>``8```8Z
`
end
chiark:~/junk>

This is a bug in tar, not cpio.  cpio writes the device number fields
using something resembling what snprintf(buf,8,"%7o\0",number) would
do if null weren't the string terminator.  (At least, I think it's
octal.)  This kind of nastiness in tar headers is common, and tar
needs to cope with it.

Ian.