The ipxitf_ioctl function in net/ipx/af_ipx.c in the Linux kernel through 4.11.1 mishandles reference counts, which allows local users to cause a denial of service (use-after-free) or possibly have unspecified other impact via a failed SIOCGIFADDR ioctl call for an IPX interface.
https://bugzilla.redhat.com/show_bug.cgi?id=1447734
https://github.com/torvalds/linux/commit/ee0d8d8482345ff97a75a7d747efc309f13b0d80