(NetBSD Issues Fix) FreeBSD Floating Point Unit Kernel Implementation Error May Let Local Users Obtain Sensitive Information
SecurityTracker Alert ID: 1016251|
SecurityTracker URL: http://securitytracker.com/id/1016251
(Links to External Site)
Date: Jun 8 2006
Disclosure of authentication information, Disclosure of system information, Disclosure of user information|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): 2.0, 2.1, 3.0|
A vulnerability was reported in FreeBSD when running on AMD processors. A local user may be able to obtain sensitive information. NetBSD is also affected.|
On "7th generation" and "8th generation" processors manufactured by AMD, the fxsave and fxrstor instructions do not save and restore the FOP, FIP, and FDP registers unless the exception summary bit (ES) in the x87 status word is set (whereas other processors store this information regardless of the ES bit).
As a result, the FreeBSD kernel does not restore the contents of the FOP, FIP, and FDP registers between context switches. This may allow a local user to monitor the execution path of a process that uses floating-point operations to obtain potentially sensitive information.
Systems that do not use AMD Athlon, Duron, Athlon MP, Athlon XP, Athlon64, Athlon64 FX, Opteron, Turion, or Sempron processors are not affected.
The vendor credits Jan Beulich with reporting this vulnerability.
A local user can monitor the execution path of a process that uses floating-point operations, which may allow the user to obtain cryptographic keys or other potentially sensitive information.|
NetBSD has released a kernel fix. NetBSD is affected by this vulnerability.|
The NetBSD advisory is available at:
Access control error|
This archive entry is a follow-up to the message listed below.|
Source Message Contents
Subject: NetBSD Security Advisory 2006-015: FPU Information leak on|
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NetBSD Security Advisory 2006-015
Topic: FPU Information leak on i386/amd64/Xen platforms with AMD CPUs
Version: NetBSD-current: source prior to April 19, 2006
NetBSD 3.0: affected
NetBSD 2.1: affected
NetBSD 2.0.*: affected
NetBSD 2.0: affected
Severity: Information leakage between local processes
Fixed: NetBSD-current: April 19, 2006
NetBSD-3-0 branch: May 12, 2006
(3.0.1 will include the fix)
NetBSD-3 branch: May 12, 2006
NetBSD-2-1 branch: May 12, 2006
(2.1.1 will include the fix)
NetBSD-2-0 branch: May 12, 2006
(2.0.4 will include the fix)
NetBSD-2 branch: May 12, 2006
Due to the documented behavior of AMD processors when running amd64, i386
and Xen NetBSD kernels, processors using floating point operations can leak
information. This may allow a local attacker to gain sensitive privileged
This vulnerability has been assigned CVE reference CVE-2006-1056.
The FXRSTOR/FXSAVE instructions on AMD processors do not restore/save the
x87 pointer registers (FOP, FIP and FDP) unless the exception summary (ES)
bit is set to 1. This potentially allows one process to discover the
stream of floating point instructions in other local processes using FPU
Solutions and Workarounds
There are no known workarounds for this issue but it only applies to i386,
amd64 and Xen NetBSD kernels when using certain AMD processors.
AMD processors known to be impacted by this issue are 7th generation (e.g.
AMD Athlon, AMD Duron, AMD Athlon MP, AMD Athlon XP, and AMD Sempron) and
8th generation (e.g. AMD Athlon64, AMD Athlon64 FX, AMD Opteron, AMD Turion,
and AMD Sempron).
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), 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/arch/i386/isa/npx.c
# cvs update -d -P sys/arch/amd64/amd64/fpu.c
# cvs update -d -P sys/arch/xen/i386/npx.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:
Christos Zoulas for implementing the fixes.
Jan Beulich is credited with discovering this issue.
Richard Brunner from AMD for providing a vendor response.
2006-06-08 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 2006, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2006-015.txt,v 1.5 2006/06/08 16:07:09 adrianp Exp $
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