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.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.