The XFS_IS_REALTIME_INODE macro in fs/xfs/xfs_linux.h in the Linux kernel before 4.13.2 does not verify that a filesystem has a realtime device, which allows local users to cause a denial of service (NULL pointer dereference and OOPS) via vectors related to setting an RHINHERIT flag on a directory.
https://access.redhat.com/errata/RHSA-2017:2918
https://bugzilla.redhat.com/show_bug.cgi?id=1491344
http://seclists.org/oss-sec/2017/q3/436
https://github.com/torvalds/linux/commit/b31ff3cdf540110da4572e3e29bd172087af65cc
http://www.debian.org/security/2017/dsa-3981
http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.13.2