The blk_rq_map_user_iov function in block/blk-map.c in the Linux kernel before 2.6.37-rc7 allows local users to cause a denial of service (panic) via a zero-length I/O request in a device ioctl to a SCSI device, related to an unaligned map.  NOTE: this vulnerability exists because of an incomplete fix for CVE-2010-4163.