The ext4 implementation in the Linux kernel before 2.6.34 does not properly track the initialization of certain data structures, which allows physically proximate attackers to cause a denial of service (NULL pointer dereference and panic) via a crafted USB device, related to the ext4_fill_super function.
https://github.com/torvalds/linux/commit/744692dc059845b2a3022119871846e74d4f6e11
https://bugzilla.redhat.com/show_bug.cgi?id=1267261
http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
http://www.openwall.com/lists/oss-security/2015/11/23/2
http://rhn.redhat.com/errata/RHSA-2016-0855.html
http://mirror.linux.org.au/linux/kernel/v2.6/ChangeLog-2.6.34