I recently completed a round of bug hunting in Linux filesystems, where I found a series of mostly minor security issues. Filesystems are a great place to start looking for kernel bugs, since the code is relatively easy to understand and review. I discovered and reported issues in btrfs (CVE-2010-1636), ext4 (CVE-2010-2066), gfs2 (CVE-2010-1641, CVE-2010-2525), and xfs (CVE-2010-2226).