The journal_unmap_buffer function in fs/jbd2/transaction.c in the Linux kernel before 3.3.1 does not properly handle the _Delay and _Unwritten buffer head states, which allows local users to cause a denial of service (system crash) by leveraging the presence of an ext4 filesystem that was mounted with a journal.
https://github.com/torvalds/linux/commit/15291164b22a357cb211b618adfef4fa82fc0de3
https://bugzilla.redhat.com/show_bug.cgi?id=749143
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.3.1
http://www.debian.org/security/2012/dsa-2469
http://secunia.com/advisories/48964
http://secunia.com/advisories/48898
http://rhn.redhat.com/errata/RHSA-2012-0670.html
http://rhn.redhat.com/errata/RHSA-2012-0571.html
http://lists.opensuse.org/opensuse-security-announce/2012-05/msg00013.html
http://lists.opensuse.org/opensuse-security-announce/2012-04/msg00021.html