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AUSCERT External Security Bulletin Redistribution
ESB-2014.1473
Multiple vulnerabilities in the compatibility layers
29 August 2014
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: kernel
Publisher: NetBSD
Operating System: UNIX variants (UNIX, Linux, OSX)
FreeBSD
NetBSD
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
Original Bulletin:
http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2014-010.txt.asc
Comment: This advisory references vulnerabilities in the NetBSD kernel that
also affect distributions other than NetBSD. It is recommended that
administrators running Linux/Unix/FreeBSD check for an updated
version of the kernel for their system.
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NetBSD Security Advisory 2014-010
=================================
Topic: Multiple vulnerabilities in the compatibility layers
Version: NetBSD-current: source prior to Tue, Apr 15th 2014
NetBSD 6.1 - 6.1.4: affected
NetBSD 6.0 - 6.0.5: affected
NetBSD 5.1 - 5.1.4: affected
NetBSD 5.2 - 5.2.2: affected
Severity: Local DoS
Fixed: NetBSD-current: Tue, Apr 15th 2014
NetBSD-6-0 branch: Mon, Apr 21th 2014
NetBSD-6-1 branch: Mon, Apr 21th 2014
NetBSD-6 branch: Mon, Apr 21th 2014
NetBSD-5-2 branch: Wed, May 14th 2014
NetBSD-5-1 branch: Wed, May 14th 2014
NetBSD-5 branch: Wed, May 14th 2014
Teeny versions released later than the fix date will contain the fix.
Please note that NetBSD releases prior to 5.1 are no longer supported.
It is recommended that all users upgrade to a supported release.
Abstract
========
Four compatibility layers are affected by several vulnerabilities:
1) FreeBSD compatibility: NULL pointer dereference
2) NetBSD 32-bit compatibility: Zero-sized memory allocation
3) Digital UNIX (formerly OSF/1) compatibility: Zero-sized
memory allocation
4) Linux and Linux 32-bit compatibility: User-controllable
kernel memory array index.
Each of them allows a local user to crash the system.
Technical Details
=================
For more clarity the four layers affected will be referred to as
COMPAT_xx, where xx is the emulated system.
1) Due to a programming mistake in COMPAT_FREEBSD, a simple call to the
sched_getparam system call would cause the kernel to dereference a
NULL pointer, and thus to crash.
2) Due to a missing input validation check in COMPAT_NETBSD32's kevent
system call, a user could cause the kernel to perform a zero-sized
memory allocation, resulting in a crash.
3) Due to a missing input validation check in COMPAT_OSF1's
getdirentries system call, a user could cause the kernel to perform
a zero-sized memory allocation, resulting in a crash.
4) Due to missing input validation checks in the COMPAT_LINUX and
COMPAT_LINUX32 ELF binary loader, a specially-crafted binary could
control a kernel memory array index - address from which data is
read. Attempting to read at an unmapped memory page will cause the
kernel to crash.
Solutions and Workarounds
=========================
- - - Disable the compability modules
- - ---------------------------------
You can achieve this with the modunload(8) tool. Please read the
appropriate manual page. For example, you can disable the Linux modules
by moving the kernel object files out of the way. These are located in:
/stand/${MACHINE_ARCH}/${KERNEL_VERSION}/modules/compat_${NAME}/compat_${NAME}.kmod
And running the following command to unload them:
# modunload compat_${NAME}
The modules have dependencies, so you need to unload them in the proper
order.
You can also disable these modules by rebuilding your kernel without the
COMPAT_${NAME} options.
Note however that it is to be considered as a temporary workaround, and
you are strongly advised to fix your system from source.
- - - Fix from source
- - -----------------
For all 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),
KERNCONF with the name of your kernel configuration file and
VERSION with the file version below
File versions containing the fixes:
FILE HEAD netbsd-6 netbsd-6-1 netbsd-6-0 netbsd-5 netbsd-5-2 netbsd-5-1
- - ---- ---- -------- ---------- ---------- -------- ---------- ----------
src/sys/compat/freebsd/freebsd_sched.c
1.20 1.19.40.1 1.19.56.1 1.19.46.1 1.19.10.1 1.19.48.1 1.19.24.1
src/sys/compat/netbsd32/netbsd32_compat_50.c
1.24 1.20.6.1 1.20.14.1 1.20.12.1 XXXXXXXX XXXXXXXXXX XXXXXXXXXX
src/sys/compat/netbsd32/netbsd32_event.c
1.11 1.9.10.2 1.9.24.1 1.9.16.1 XXXXXXXX XXXXXXXXXX XXXXXXXXXX
src/sys/compat/osf1/osf1_file.c
1.42 % % % XXXXXXXX XXXXXXXXXX XXXXXXXXXX
src/sys/compat/linux/common/linux_exec_elf32.c
1.91 1.86.2.1 1.86.16.1 1.86.8.1 1.81.10.1 1.81.20.1 1.81.16.1
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update -d -P -r VERSION sys/compat/freebsd/freebsd_sched.c
# cvs update -d -P -r VERSION sys/compat/netbsd32/netbsd32_compat_50.c
# cvs update -d -P -r VERSION sys/compat/netbsd32/netbsd32_event.c
# cvs update -d -P -r VERSION sys/compat/osf1/osf1_file.c
# cvs update -d -P -r VERSION sys/compat/linux/common/linux_exec_elf32.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 Maxime Villard, Christos Zoulas, Martin Husemann, Chuck
Silvers, Enami Tsugutomo and Matt Thomas for finding, fixing and
helping in fixing these issues.
Revision History
================
2014-08-27 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-SA2014-010.txt.asc
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .
Copyright 2014, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2014-010.txt,v 1.1 2014/08/27 00:26:00 tonnerre Exp $
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