kernel: jbd2: unmapped buffer with _Unwritten or _Delay flags set can lead to DoS

The journalunmapbuffer 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 ...