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FreeBSD-EN-09:01.kenv Errata Notice
The FreeBSD Project
Topic: Kernel panic when dumping environment
Category: core
Module: kern
Announced: 2009-03-23
Affects: FreeBSD 7.x
Corrected: 2009-03-23 00:00:50 UTC (RELENG_7, 7.2-PRERELEASE)
2009-03-23 00:00:50 UTC (RELENG_7_1, 7.1-RELEASE-p4)
2009-03-23 00:00:50 UTC (RELENG_7_0, 7.0-RELEASE-p11)
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit .
I. Background
The kenv(2) system call allows userland processes to get, set, and unset
kernel environment variables, as well as to dump all of the entries in
the kernel environment.
II. Problem Description
When dumping all of the entries in the kernel environment, the kernel
does not adequately bounds-check the size of the buffer into which the
environment should be written.
III. Impact
An unprivileged process can cause the FreeBSD kernel to attempt to
allocate a very large amount of memory, thereby causing the FreeBSD
kernel to panic.
IV. Workaround
No workaround is available, but systems without untrusted local users
are not vulnerable.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_1
or RELENG_7_0 security branch dated after the correction date.
2) To patch your present system:
The following patch has been verified to apply to FreeBSD 7.0 and 7.1
systems.
a) Download the patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/EN-09:01/kenv.patch
# fetch http://security.FreeBSD.org/patches/EN-09:01/kenv.patch.asc
b) Apply the patch.
# cd /usr/src
# patch < /path/to/patch
c) Recompile your kernel as described in
and reboot the
system.
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
CVS:
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_7
src/sys/kern/kern_environment.c 1.47.2.1
RELENG_7_1
src/UPDATING 1.507.2.13.2.7
src/sys/conf/newvers.sh 1.72.2.9.2.8
src/sys/kern/kern_environment.c 1.47.6.2
RELENG_7_0
src/UPDATING 1.507.2.3.2.15
src/sys/conf/newvers.sh 1.72.2.5.2.15
src/sys/kern/kern_environment.c 1.47.4.1
- -------------------------------------------------------------------------
Subversion:
Branch/path Revision
- -------------------------------------------------------------------------
stable/7/ r190301
releng/7.1/ r190301
releng/7.0/ r190301
- -------------------------------------------------------------------------
VII. References
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-EN-09:01.kenv.asc
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