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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D61DC001DE for ; Tue, 25 Jul 2023 10:40:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232075AbjGYKkO (ORCPT ); Tue, 25 Jul 2023 06:40:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233678AbjGYKkK (ORCPT ); Tue, 25 Jul 2023 06:40:10 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78708194; Tue, 25 Jul 2023 03:40:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1690281609; x=1721817609; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=Jyr/C0uXdLTqSt8o11IlypH7yijyNPTn5qF6VHkHyus=; b=DPa+kMGng0tg+AHH8bKL35qpQlBHWUzmy3JWisZeMHLINiPdFvyRJ9XU fddPuQQc4vdp5/4XmwCHRxdsaXxgdN3XLRl+Mz67yewakXaxwlULSfKx3 lvDUG4K+YbTyUiAMmNsbrf9yqtFmnPj540mVese/CqIZPx+Wix/3TERI7 Nzpx6QqhAC7gGJfX2/nN42ESGjG7SetGuQ/Wp8NqwNCeLflp3dIflB29h L/PyHnBB92t0bEg6ak+iHtNs2ywpC70NTPw/XVxgcRiS1gz1HH4nMZosM AWOdn15yoQP38E01Ff+0aB5DOKK0BRwi955bew9ez1AfQuMQmLeee/ZiC g==; X-IronPort-AV: E=McAfee;i="6600,9927,10781"; a="352583079" X-IronPort-AV: E=Sophos;i="6.01,230,1684825200"; d="scan'208";a="352583079" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jul 2023 03:39:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10781"; a="791330038" X-IronPort-AV: E=Sophos;i="6.01,230,1684825200"; d="scan'208";a="791330038" Received: from hegang-mobl.ccr.corp.intel.com (HELO localhost) ([10.254.212.56]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jul 2023 03:39:48 -0700 Date: Tue, 25 Jul 2023 18:39:45 +0800 From: Yu Zhang To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Reima Ishii Subject: Re: [PATCH 3/5] KVM: x86/mmu: Harden TDP MMU iteration against root w/o shadow page Message-ID: <20230725103945.wfa5zdupen3oo6xl@linux.intel.com> References: <20230722012350.2371049-1-seanjc@google.com> <20230722012350.2371049-4-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230722012350.2371049-4-seanjc@google.com> User-Agent: NeoMutt/20171215 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 21, 2023 at 06:23:48PM -0700, Sean Christopherson wrote: > Explicitly check that tdp_iter_start() is handed a valid shadow page > to harden KVM against bugs where Sorry, where? It's not about guest using an invisible GFN, it's about a KVM bug, right? > > Opportunistically stop the TDP MMU iteration instead of continuing on > with garbage if the incoming root is bogus. Attempting to walk a garbage > root is more likely to caused major problems than doing nothing. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/mmu/tdp_iter.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c > index d2eb0d4f8710..bd30ebfb2f2c 100644 > --- a/arch/x86/kvm/mmu/tdp_iter.c > +++ b/arch/x86/kvm/mmu/tdp_iter.c > @@ -39,13 +39,14 @@ void tdp_iter_restart(struct tdp_iter *iter) > void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root, > int min_level, gfn_t next_last_level_gfn) > { > - int root_level = root->role.level; > - > - WARN_ON(root_level < 1); > - WARN_ON(root_level > PT64_ROOT_MAX_LEVEL); > + if (WARN_ON_ONCE(!root || (root->role.level < 1) || > + (root->role.level > PT64_ROOT_MAX_LEVEL))) { > + iter->valid = false; > + return; > + } > I saw many usages of WARN_ON_ONCE() and WARN_ON() in KVM. And just wonder, is there any criteria for KVM when to use which? B.R. Yu