On Wed, Feb 21, 2018 at 01:59:55PM -0600, Brijesh Singh wrote: > Sure, checking access_ok() does not guarantee that later > copy_from_user() will not fail. But it does eliminate one possible > reason for the failure. We are trying to validate most of the user > inputs before we invoke SEV command. That makes no sense whatsoever. If user is deliberately fuzzing your code or trying to DoS it, that "validation" doesn't buy you anything - they can just as well feed you NULL, after all. What is the rationale for that? "Userland is accidentally feeding us garbage pointers" is the case where slowness is the least of your concerns...
