Archive for February, 2008

Going to FOSDEM 08

Wednesday, February 20th, 2008


I’ll be at FOSDEM this weekend. Please say hello if you find me.

Critical Linux kernel vmsplice security issues

Monday, February 11th, 2008

There have been 2 significant security flaws found in the Linux kernel, accompanied by plenty of misinformation and confusion. This is my attempt to clear things up a bit.

The short story: If you are running Linux 2.6.17 or newer then any user who has local console or SSH terminal access to your machine can easily become root or crash the system. If this is a problem for you, then you need to upgrade to gentoo-sources-2.6.23-r8 or gentoo-sources-2.6.24-r2. At the time of writing, there are no official released upstream kernels which solve the issues – Linux 2.6.24.1 and 2.6.23.15 are vulnerable.

The longer story:

There are actually two separate security issues in question here. However, they both have the same impact (any user can adjust kernel memory and hence become root), and both issues exist within the implementation of the vmsplice() system call. vmsplice() was added in Linux 2.6.17 and is built into every kernel build – there is no configuration option to exclude vmsplice. Two separate exploits have been publicly released which exploit each of the two issues respectively.

The first security issue under discussion was added in Linux 2.6.23 (obviously unintentionally!). This means that 2.6.22 and older are not vulnerable to the first exploit. This issue was fixed by this patch in Linux 2.6.23.15 and Linux 2.6.24.1. This vulnerability has been classified with two codes: CVE-2008-0009 and CVE-2008-0010.

The second security issue is more serious. Firstly, it has existed for the entire lifetime of vmsplice() which means that any kernel version 2.6.17 or newer is vulnerable. Secondly, it is not fixed in any upstream kernel release at time of writing, but the fix has been merged into Linus’ upstream development tree. This vulnerability has been assigned ID CVE-2008-0600.

gentoo-sources-2.6.23-r7 and gentoo-sources-2.6.24-r1 include the fix for the first issue, but are still vulnerable to the second (which is equally serious).

gentoo-sources-2.6.23-r8 and gentoo-sources-2.6.24-r2 include the fix for the second issue and are hence secured against all known vmsplice exploits at this point in time. 2.6.23-r8 will be marked stable when I wake up 7-8 hours from now, so testing of that release would be appreciated.

UPDATE: gentoo-sources-2.6.23-r8 is now stable, and upstream have also released the following which fix all currently known issues: Linux 2.6.23.16, 2.6.24.2 and 2.6.25-rc1.

Project repositories moved

Friday, February 1st, 2008

Steve Berryman has been kindly hosting the code for some of my projects since the end of 2006 (dsd.object4.net). The server is going away now, so it’s time to move.

My new home is kindly hosted by Ryan Gibbons and is accessible at http://projects.reactivated.net. My git repositories are no longer available over http, they are instead accessible through git://projects.reactivated.net/~dsd/PROJECTNAME
gitweb is also available as before, and nightly snapshots for some projects will be generated here.

Many thanks for Steve and now Ryan for taking this administrative workload off my back and allowing me to focus on developing the software!