Multiple buffer underflows in the XFS implementation in the Linux kernel through 3.12.1 allow local users to cause a denial of service (memory corruption) or possibly have unspecified other impact by leveraging the CAP_SYS_ADMIN capability for a (1) XFS_IOC_ATTRLIST_BY_HANDLE or (2) XFS_IOC_ATTRLIST_BY_HANDLE_32 ioctl call with a crafted length value, related to the xfs_attrlist_by_handle function in fs/xfs/xfs_ioctl.c and the xfs_compat_attrlist_by_handle function in fs/xfs/xfs_ioctl32.c.