fs/ext4/extents.c in the Linux kernel before 3.0 does not mark a modified extent as dirty in certain cases of extent splitting, which allows local users to cause a denial of service (system crash) via vectors involving ext4 umount and mount operations.
https://github.com/torvalds/linux/commit/667eff35a1f56fa74ce98a0c7c29a40adc1ba4e3
https://bugzilla.redhat.com/show_bug.cgi?id=747942