net/ipv4/route.c in the Linux kernel 4.13-rc1 through 4.13-rc6 is too
late to check for a NULL fi field when RTM_F_FIB_MATCH is set, which
allows local users to cause a denial of service (NULL pointer
dereference) or possibly have unspecified other impact via crafted
system calls. NOTE: this does not affect any stable release.