From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933158AbeBVP5J (ORCPT ); Thu, 22 Feb 2018 10:57:09 -0500 Received: from mail-by2nam01on0087.outbound.protection.outlook.com ([104.47.34.87]:26624 "EHLO NAM01-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932952AbeBVP5F (ORCPT ); Thu, 22 Feb 2018 10:57:05 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=brijesh.singh@amd.com; Cc: brijesh.singh@amd.com, kvm@vger.kernel.org, Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Borislav Petkov , Tom Lendacky , linux-kernel@vger.kernel.org, Joerg Roedel Subject: Re: [PATCH] KVM: SVM: Fix sparse: incorrect type in argument 1 (different base types) To: Al Viro References: <20180219161228.46931-1-brijesh.singh@amd.com> <20180221174910.GI30522@ZenIV.linux.org.uk> <20180221201839.GK30522@ZenIV.linux.org.uk> From: Brijesh Singh Message-ID: Date: Thu, 22 Feb 2018 09:56:57 -0600 User-Agent: Mozilla/5.0 (X11; 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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. > Currently, we let user query the blob length with params.len == 0 || param.uaddr == NULL. We could limit it to just params.len == 0. > What is the rationale for that? "Userland is accidentally feeding > us garbage pointers" is the case where slowness is the least of your > concerns... > My intent was to do some obvious failure checks on user inputs before invoking the HW. I do see your point that if userspace is feeding us garbage then slowness is least of our concern. If you think that we should not be using access_ok() in this particular case then I am okay with it.