The tunnels implementation in the Linux kernel before 2.6.34, when tunnel functionality is configured as a module, allows remote attackers to cause a denial of service (OOPS) by sending a packet during module loading.
https://bugzilla.redhat.com/show_bug.cgi?id=702303
http://www.openwall.com/lists/oss-security/2011/05/05/6
http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.34