An issue was discovered in the Linux kernel through 5.11.6. fastrpc_internal_invoke in drivers/misc/fastrpc.c does not prevent user applications from sending kernel RPC messages, aka CID-20c40794eb85. This is a related issue to CVE-2019-2308.
https://security.netapp.com/advisory/ntap-20210401-0003/
https://lore.kernel.org/stable/YD03ew7+6v0XPh6l%40kroah.com/
https://git.kernel.org/linus/20c40794eb85ea29852d7bc37c55713802a543d6