bin/189284: dd(1): may write junk if conv=sparse with obs < ibs

[Thomas Quinot]

>Number:         189284
>Category:       bin
>Synopsis:       dd(1): may write junk if conv=sparse with obs < ibs
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat May 03 11:40:00 UTC 2014
>Closed-Date:
>Last-Modified:
>Originator:     Thomas Quinot
>Release:        FreeBSD 9.2-STABLE amd64
>Organization:
>Environment:
System: FreeBSD melamine.cuivre.fr.eu.org 9.2-STABLE FreeBSD 9.2-STABLE #0 r256080: Sun Oct 6 15:33:30 CEST 2013 thomas at melamine.cuivre.fr.eu.org:/usr/obj/users/thomas/projects/FreeBSD/base/stable/9/sys/GENERIC amd64


	
>Description:
	When ibs is an integral multiple of ibs, and there is a sequence
	of obs consecutive zeroes at the end of the last input block,
	the last character written by dd may be some different (non-zero)
	byte from the input stream.
>How-To-Repeat:

$ perl -e 'print "ABCDEFGH\0\0\0\0\0\0\0\0"'|dd ibs=16 obs=8 conv=sparse of=toto 
1+0 records in
2+0 records out
16 bytes transferred in 0.001373 secs (11653 bytes/sec)
$ od -a toto
0000000    A   B   C   D   E   F   G   H nul nul nul nul nul nul nul   A
0000020

>Fix:

	


>Release-Note:
>Audit-Trail:
>Unformatted: