The fuse_ioctl_copy_user function in the ioctl handler in fs/fuse/file.c in the Linux kernel 2.6.29-rc1 through 2.6.30.y uses the wrong variable in an argument to the kunmap function, which allows local users to cause a denial of service (panic) via unknown vectors.
https://www.redhat.com/archives/fedora-package-announce/2009-December/msg01344.html
https://bugzilla.redhat.com/show_bug.cgi?id=549400
http://www.securityfocus.com/bid/37453
http://www.openwall.com/lists/oss-security/2009/12/23/1