NetBSD Security Advisory 2013-001: kernel panic triggered from userland

[NetBSD Security Officer <security-officer%NetBSD.org@localhost>]

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                 NetBSD Security Advisory 2013-001
                 =================================

Topic:          kernel panic triggered from userland

Version:        NetBSD-current:         affected prior to Dec 29th, 2012
                NetBSD 6.0.*:           affected
                NetBSD 6.0:             affected
                NetBSD 5.1.*:           not affected
                NetBSD 5.0.*:           not affected
                NetBSD 5.0:             not affected

Severity:       Local system crash

Fixed:          NetBSD-current:         Dec 29th, 2012
                NetBSD-6-0 branch:      Jan 7th, 2013
                NetBSD-6 branch:        Jan 7th, 2013

Please note that NetBSD releases prior to 5.0 are no longer supported.
It is recommended that all users upgrade to a supported release.


Abstract
========

A user can panic the machine by using ktrace or ktruss on
a program sleeping in recvmsg.


Technical Details
=================

If an untraced process sleeps in recvmsg/sendmsg, the syscall does not
allocate an iov structure for ktrace. When tracing is then enabled
and the process wakes up, it crashes the kernel.

A local user could intentionally crash the machine by running a
program that entered the required sleep state, and then call ktrace
or ktruss on it.


Solutions and Workarounds
=========================

The following versions contain the fix:

src/sys/kern/uipc_syscalls.c
        HEAD            1.158
        netbsd-6        1.154.2.2
        netbsd-6-0      1.154.2.1.4.1

For all affected NetBSD versions, you need to obtain fixed kernel
sources, rebuild and install the new kernel, and reboot the system.
                                      
The fixed source may be obtained from the NetBSD CVS repository.        
The following instructions briefly summarise how to upgrade your        
kernel.  In these instructions, replace:

  ARCH     with your architecture (from uname -m), and                  
  KERNCONF with the name of your kernel configuration file.    

To update from CVS, re-build, and re-install the kernel:

        # cd src
        # cvs update -d -P sys/kern/uipc_syscalls.c
        # ./build.sh kernel=KERNCONF
        # mv /netbsd /netbsd.old
        # cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd 
        # shutdown -r now

For more information on how to do this, see:    

   http://www.NetBSD.org/guide/en/chap-kernel.html


Thanks To
=========

Thanks to Michael van Elst for finding and fixing this problem.


Revision History
================

        2013-01-28      Initial release


More Information
================

Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at 
  http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2013-001.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .

Copyright 2013, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$NetBSD: NetBSD-SA2013-001.txt,v 1.1 2013/01/28 11:12:51 tonnerre Exp $

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