From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35702C433B4 for ; Mon, 3 May 2021 21:17:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1326961283 for ; Mon, 3 May 2021 21:17:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229693AbhECVSg (ORCPT ); Mon, 3 May 2021 17:18:36 -0400 Received: from smtp-fw-4101.amazon.com ([72.21.198.25]:33927 "EHLO smtp-fw-4101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229499AbhECVSg (ORCPT ); Mon, 3 May 2021 17:18:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazon201209; t=1620076663; x=1651612663; h=date:from:to:cc:message-id:references:mime-version: in-reply-to:subject; bh=04TqWL9x3kySh2dDc818s2E7ADPYmdphIO/5JHsPMSc=; b=rH+QVhBhwaJS+0U5EPixs8azYWre4dvVBrbNTeKgDbbbyyHKUrDza3vx Zmk2hehkk94dkLHt0QLneMQS3vJ4f4QPVJSuD+6oazt92nc+L+SvogcXR 4B0lxhPRa9V1iy13uiAkGLYeGeDlzw49PbG9R9KlWgrq6oK1SdifRWuTe Q=; X-IronPort-AV: E=Sophos;i="5.82,271,1613433600"; d="scan'208";a="105449271" Subject: Re: [PATCH] KVM: x86: Hoist input checks in kvm_add_msr_filter() Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-2b-8cc5d68b.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-4101.iad4.amazon.com with ESMTP; 03 May 2021 21:17:35 +0000 Received: from EX13D28EUC003.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-2b-8cc5d68b.us-west-2.amazon.com (Postfix) with ESMTPS id 02C54A059E; Mon, 3 May 2021 21:17:32 +0000 (UTC) Received: from uc8bbc9586ea454.ant.amazon.com (10.43.162.28) by EX13D28EUC003.ant.amazon.com (10.43.164.43) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 May 2021 21:17:27 +0000 Date: Mon, 3 May 2021 23:17:23 +0200 From: Siddharth Chandrasekaran To: Sean Christopherson CC: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , , "H. Peter Anvin" , , Message-ID: <20210503211722.GA8688@uc8bbc9586ea454.ant.amazon.com> References: <20210503122111.13775-1-sidcha@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.43.162.28] X-ClientProxiedBy: EX13D18UWA003.ant.amazon.com (10.43.160.238) To EX13D28EUC003.ant.amazon.com (10.43.164.43) Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, May 03, 2021 at 08:53:09PM +0000, Sean Christopherson wrote: > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > On Mon, May 03, 2021, Siddharth Chandrasekaran wrote: > > In ioctl KVM_X86_SET_MSR_FILTER, input from user space is validated > > after a memdup_user(). For invalid inputs we'd memdup and then call > > kfree unnecessarily. Hoist input validation to avoid kfree altogether. > > > > Signed-off-by: Siddharth Chandrasekaran > > --- > > arch/x86/kvm/x86.c | 21 ++++++--------------- > > 1 file changed, 6 insertions(+), 15 deletions(-) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index ee0dc58ac3a5..15c20b31cc91 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -5393,11 +5393,16 @@ static int kvm_add_msr_filter(struct kvm_x86_msr_filter *msr_filter, > > struct msr_bitmap_range range; > > unsigned long *bitmap = NULL; > > size_t bitmap_size; > > - int r; > > > > if (!user_range->nmsrs) > > return 0; > > > > + if (user_range->flags & ~(KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE)) > > + return -EINVAL; > > + > > + if (!user_range->flags) > > + return -EINVAL; > > + > > bitmap_size = BITS_TO_LONGS(user_range->nmsrs) * sizeof(long); > > if (!bitmap_size || bitmap_size > KVM_MSR_FILTER_MAX_BITMAP_SIZE) > > return -EINVAL; > > @@ -5413,24 +5418,10 @@ static int kvm_add_msr_filter(struct kvm_x86_msr_filter *msr_filter, > > .bitmap = bitmap, > > }; > > > > - if (range.flags & ~(KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE)) { > > - r = -EINVAL; > > - goto err; > > - } > > - > > - if (!range.flags) { > > - r = -EINVAL; > > - goto err; > > - } > > - > > - /* Everything ok, add this range identifier. */ > > msr_filter->ranges[msr_filter->count] = range; > > Might be worth elminating the intermediate "range", too. Doesn't affect output, > but it would make it a little more obvious that the new range is mostly coming > straight from userspace input. E.g. > > msr_filter->ranges[msr_filter->count] = (struct msr_bitmap_range) { > .flags = user_range->flags, > .base = user_range->base, > .nmsrs = user_range->nmsrs, > .bitmap = bitmap, > }; > > Either way: > > Reviewed-by: Sean Christopherson Thanks for the review. Changed as suggested. ~ Sid. Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879