A double-free can happen in idr_remove_all() in lib/idr.c in the Linux kernel 2.6 branch. An unprivileged local attacker can use this flaw for a privilege escalation or for a system crash and a denial of service (DoS).
https://support.f5.com/csp/article/K04327111
https://security.netapp.com/advisory/ntap-20190710-0002/