kern/40575: security.pax.aslr breaks tar -z

[bouyer%antioche.lip6.fr@localhost]

>Number:         40575
>Category:       kern
>Synopsis:       security.pax.aslr breaks tar -z
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 07 19:25:00 +0000 2009
>Originator:     Manuel Bouyer
>Release:        NetBSD 5.0_RC1
>Organization:
>Environment:
System: NetBSD antioche.lip6.fr 5.0_RC1 NetBSD 5.0_RC1 (ANTIOCHE5-64) #5: Sat 
Feb 7 15:51:51 CET 2009 
bouyer@roll:/dsk/l1/misc/bouyer/tmp/amd64/obj/dsk/l1/misc/bouyer/netbsd-5/src/sys/arch/amd64/compile/ANTIOCHE5-64
 amd64
Architecture: x86_64
Machine: amd64
>Description:
        antioche:/home/ftp/pub/pkgsrc/packages/NetBSD/x86_64/5.0/All#sysctl -w 
security.pax.aslr.global=1
        security.pax.aslr.global: 0 -> 1
        antioche:/home/ftp/pub/pkgsrc/packages/NetBSD/x86_64/5.0/All#tar tzvf 
ttcp-1.12nb2.tgz
        tar: End of archive volume 1 reached
        tar: Sorry, unable to determine archive format.
        antioche:/home/ftp/pub/pkgsrc/packages/NetBSD/x86_64/5.0/All#sysctl -w 
security.pax.aslr.global=0
        security.pax.aslr.global: 1 -> 0
        antioche:/home/ftp/pub/pkgsrc/packages/NetBSD/x86_64/5.0/All#tar tzvf 
ttcp-1.12nb2.tgz
        -rw-r--r--  1 root     wheel        430 Jan 16 14:43 +CONTENTS
        -r--r--r--  1 root     wheel         43 Jan 16 14:43 +COMMENT
        -r--r--r--  1 root     wheel        364 Jan 16 14:43 +DESC
        -rw-r--r--  1 root     wheel        424 Jan 16 14:43 +BUILD_VERSION
        -rw-r--r--  1 root     wheel       1906 Jan 16 14:43 +BUILD_INFO
        -rw-r--r--  1 root     wheel          6 Jan 16 14:43 +SIZE_PKG
        -rw-r--r--  1 root     wheel          2 Jan 16 14:43 +SIZE_ALL
        -r-xr-xr-x  1 root     wheel      20408 Jan 16 14:43 bin/ttcp
        -r--r--r--  1 root     wheel       4761 Jan 16 14:43 man/cat1/ttcp.0
        -r--r--r--  1 root     wheel       3885 Jan 16 14:43 man/man1/ttcp.1
        tar: ustar vol 1, 10 files, 40960 bytes read, 0 bytes written in 1 secs 
(40960 bytes/sec)

        I tracked this down to the read() from the tar's side of the pipe
        with gzip returning 0, before gzip has even started.
        A zcat | tar works fine.
        This is only dependant on security.pax.aslr, other
        security.pax settings have no influence.
>How-To-Repeat:
        set security.pax.aslr.global=1, try  to use tar -z
>Fix:
        workaround: don't set security.pax.aslr.global to 1