August 19, 2009

Slackware Security Announcement: 2009-08-18 kernel (SSA:2009-230-01)

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:

Here are the details from the Slackware 12.2 ChangeLog:



Added new kernels and kernel packages for Linux 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:

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


(* Security fix *)


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 Give a try. This is another primary FTP site for Slackware that can be considerably faster than downloading directly from

Thanks to the friendly folks at the OSU Open Source Lab ( for donating additional FTP and rsync hosting to the Slackware project! :-) Also see the "Get Slack" section on for additional mirror sites near you.

Updated kernel packages for Slackware 12.2 may be found here:

Updated kernel packages for Slackware -current may be found here:

Updated kernel packages for Slackware64 -current may be found here:

Hotfix/init script packages to increase mmap_min_addr to 4096:

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



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:

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-

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


Slackware Linux Security Team
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