kernel

2009-08-1820:47:47

Slackware Linux Project

www.slackware.com

EPSS

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New Linux kernel packages are available for Slackware 12.2 and -current
to address a security issue. A kernel bug discovered by Tavis Ormandy
and Julien Tinnes of the Google Security Team could allow a local user
to fill memory page zero with arbitrary code and then use the kernel
sendpage operation to trigger a NULL pointer dereference, executing the
code in the context of the kernel. If successfully exploited, this bug
can be used to gain root access.

At this time we have prepared fixed kernels for the stable version of
Slackware (12.2), as well as for both 32-bit x86 and x86_64 -current
versions. Additionally, we have added a package to the /patches
directory for Slackware 12.1 and 12.2 that will set the minimum memory
page that can be mmap()ed from userspace without additional privileges
to 4096. The package will work with any kernel supporting the
vm.mmap_min_addr tunable, and should significantly reduce the potential
harm from this bug, as well as future similar bugs that might be found
in the kernel. More updated kernels may follow.

For more information, see:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2692

Here are the details from the Slackware 12.2 ChangeLog:

patches/packages/linux-2.6.27.31/:
Added new kernels and kernel packages for Linux 2.6.27.31 to address
a bug in proto_ops structures which could allow a user to use the
kernel sendpage operation to execute arbitrary code in page zero.
This could allow local users to gain escalated privileges.
This flaw was discovered by Tavis Ormandy and Julien Tinnes of the
Google Security Team.
For more information, see:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2692
In addition, these kernels change CONFIG_DEFAULT_MMAP_MIN_ADDR kernel
config option value to 4096, which should prevent the execution of
arbitrary code by future NULL dereference bugs that might be found in
the kernel. If you are compiling your own kernel, please check this
option in your .config. If it is set to =0, you may wish to edit it
to 4096 (or some other value > 0) and then reconfigure, or the kernel
will not have default protection against zero page attacks from
userspace.
(* Security fix )
patches/packages/kernel-mmap_min_addr-4096-noarch-1.tgz:
This package adds an init script to edit /etc/sysctl.conf, adding
this config option:
vm.mmap_min_addr = 4096
This will configure the kernel to disallow mmap() to userspace of any
page lower than 4096, preventing privilege escalation by CVE-2009-2692.
This is a hot fix package and will take effect immediately upon
installation on any system running a kernel that supports configurable
/proc/sys/vm/mmap_min_addr (kernel 2.6.23 or newer).
( Security fix *)

Where to find the new packages:

HINT: Getting slow download speeds from ftp.slackware.com?
Give slackware.osuosl.org a try. This is another primary FTP site
for Slackware that can be considerably faster than downloading
directly from ftp.slackware.com.

Thanks to the friendly folks at the OSU Open Source Lab
(http://osuosl.org) for donating additional FTP and rsync hosting
to the Slackware project! :-)

Also see the "Get Slack" section on http://slackware.com for
additional mirror sites near you.

Updated kernel packages for Slackware64 -current may be found here:
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/a/kernel-firmware-2.6.29.6-noarch-2.txz
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/a/kernel-generic-2.6.29.6-x86_64-2.txz
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/a/kernel-huge-2.6.29.6-x86_64-2.txz
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/a/kernel-modules-2.6.29.6-x86_64-2.txz
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/d/kernel-headers-2.6.29.6-x86-2.txz
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/k/kernel-source-2.6.29.6-noarch-2.txz

Hotfix/init script packages to increase mmap_min_addr to 4096:
ftp://ftp.slackware.com/pub/slackware/slackware-12.1/patches/packages/kernel-mmap_min_addr-4096-noarch-1.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-12.2/patches/packages/kernel-mmap_min_addr-4096-noarch-1.tgz

These packages are the same, and will work with any 2.6.23 or newer kernel.

Signatures:

All packages are signed with the Slackware Security Team GPG signature for
verification of authenticity. File may also be checked with the CHECKSUMS.md5
file provided in each Slackware directory tree, which is also signed with the
Slackware GPG key.

Kernel patches for Linux 2.4.x and Linux 2.6.x:

Kernel patches for CVE-2009-2692 that should apply cleanly to most 2.4
and 2.6 kernel source may be found here:

ftp://ftp.slackware.com/pub/slackware/unsupported/kernel-patches/linux-2.4.x-CVE-2009-2692.diff.gz
ftp://ftp.slackware.com/pub/slackware/unsupported/kernel-patches/linux-2.6.x-CVE-2009-2692.diff.gz

Installation instructions:

Upgrade the kernel packages as root, rebuild the initrd with
mkinitrd, and reinstall LILO. For details on the process of
updating the Slackware 12.2 kernels, see the README file in
/patches/packages/linux-2.6.27.31/.

To activate the mmap_min_addr protection in your /etc/sysctl.conf
for 2.6.23 or newer kernels, simply install the package:

installpkg kernel-mmap_min_addr-4096-noarch-1.tgz

If you are building your own kernel from unfixed vanilla sources,
the patch appropriate for your kernel may be applied to the source
like this:

cd /usr/src/linux
zcat linux-2.6.x-CVE-2009-2692.diff.gz | patch -p1 --verbose