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AUSCERT External Security Bulletin Redistribution
kernel panic triggered from userland
29 January 2013
AusCERT Security Bulletin Summary
Operating System: NetBSD
Impact/Access: Denial of Service -- Existing Account
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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.
A user can panic the machine by using ktrace or ktruss on
a program sleeping in recvmsg.
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:
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:
Thanks to Michael van Elst for finding and fixing this problem.
2013-01-28 Initial release
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
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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