Add better sanity checking to the logic that handles ioctl processing for nfsclient and nfs4client in order to prevent local root users from panicing the system.
Add better sanity checking to the logic that handles ioctl processing
for nfsclient and nfs4client in order to prevent local root users
from panicing the system.

PR:		kern/77463
Submitted by:	Wojciech A. Koszek
Reviewed by:	cel, rees
MFC after:	2 weeks
Security:	Local root users can panic the system at will

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