The ext4_fill_super function in fs/ext4/super.c in the Linux kernel before 2.6.39 does not properly initialize a certain error-report data structure, which allows local users to cause a denial of service (OOPS) by attempting to mount a crafted ext4 filesystem.
https://github.com/torvalds/linux/commit/0449641130f5652b344ef6fa39fa019d7e94660a
https://euvd.enisa.europa.eu/vulnerability/EUVD-2011-2480
http://www.openwall.com/lists/oss-security/2011/06/24/4
http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39