From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f179.google.com (mail-pg1-f179.google.com [209.85.215.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2A00173 for ; Wed, 18 Aug 2021 23:06:41 +0000 (UTC) Received: by mail-pg1-f179.google.com with SMTP id e7so3958351pgk.2 for ; Wed, 18 Aug 2021 16:06:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6LXlTnktuLXOSEatHkAd9iidtx/DlqNXw6t+P+U3BQc=; b=QDNt5PHgo+7rFQ5/N15pMYx2nigmnDuCuJ+bOuvXfS72zqVl8vZRlj8bX+wFTjLeE1 +cWdQw4DYXF54Bu3mpVNecT17rymK4/4HID0NO8YPAsOH71eiDyu8sN6XAFVcXLqPAMH GiSiCnGqiMI57DyQ0LAdNhljzGxXXxsfxTLco= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=6LXlTnktuLXOSEatHkAd9iidtx/DlqNXw6t+P+U3BQc=; b=WGJYLpRymHUl19AciSfhsvPL5VMzfUXO+ye85jb+8S7NIvuVyx4XwwLL+7lcIjCXsc E61eQy6TUiZK8PSFumip/Xx3fjk/SBl+EKOhrS/VojuY60fKVTwAjQoMmO/XruaMBLm4 +wdQ9dYoLUCRGaHh20caY8galf4e4rzWkRv6lTDjEIC9QHkjIvt7+QOCPZsJUrL0djN1 ZTZkR9eN//DqwJp1BHCu+oFoVexeWvhoJV1RwIADUkyDDmsuVMobFjneMQGP62junWIA XmOrsVxL5ADcAFvJAthmkoV7jc0R1093JiugMs8PlfViIr0X005dPdOte5hV+ZA8ghk7 08Og== X-Gm-Message-State: AOAM5338TtOci3/PVCT8As+Zja5u2HyZtikm3gNI4fpE1VZZ/hbWLd3N MljrQefPupqPeAm3BIytG7sP7Q== X-Google-Smtp-Source: ABdhPJyUYId4jZehTEC5dWKrbyuUEowd9b0WCT527H1rHej12/Bkc/D16VHqxCGKKKhtIhB0IMVa/w== X-Received: by 2002:aa7:8242:0:b0:3e2:97eb:d6e8 with SMTP id e2-20020aa78242000000b003e297ebd6e8mr9677080pfn.66.1629328001407; Wed, 18 Aug 2021 16:06:41 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id 143sm916287pfz.13.2021.08.18.16.06.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Aug 2021 16:06:40 -0700 (PDT) Date: Wed, 18 Aug 2021 16:06:39 -0700 From: Kees Cook To: Sean Christopherson Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, "Gustavo A. R. Silva" , Greg Kroah-Hartman , Andrew Morton , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, Rasmus Villemoes , linux-hardening@vger.kernel.org Subject: Re: [PATCH v2 53/63] KVM: x86: Use struct_group() to zero decode cache Message-ID: <202108181605.44C504C@keescook> References: <20210818060533.3569517-1-keescook@chromium.org> <20210818060533.3569517-54-keescook@chromium.org> <202108180922.6C9E385A1@keescook> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Aug 18, 2021 at 10:53:58PM +0000, Sean Christopherson wrote: > On Wed, Aug 18, 2021, Kees Cook wrote: > > On Wed, Aug 18, 2021 at 03:11:28PM +0000, Sean Christopherson wrote: > > > From dbdca1f4cd01fee418c252e54c360d518b2b1ad6 Mon Sep 17 00:00:00 2001 > > > From: Sean Christopherson > > > Date: Wed, 18 Aug 2021 08:03:08 -0700 > > > Subject: [PATCH] KVM: x86: Replace memset() "optimization" with normal > > > per-field writes > > > > > > Explicitly zero select fields in the emulator's decode cache instead of > > > zeroing the fields via a gross memset() that spans six fields. gcc and > > > clang are both clever enough to batch the first five fields into a single > > > quadword MOV, i.e. memset() and individually zeroing generate identical > > > code. > > > > > > Removing the wart also prepares KVM for FORTIFY_SOURCE performing > > > compile-time and run-time field bounds checking for memset(). > > > > > > No functional change intended. > > > > > > Reported-by: Kees Cook > > > Signed-off-by: Sean Christopherson > > > > Reviewed-by: Kees Cook > > > > Do you want me to take this patch into my tree, or do you want to carry > > it for KVM directly? > > That's a Paolo question :-) > > What's the expected timeframe for landing stricter bounds checking? If it's > 5.16 or later, the easiest thing would be to squeak this into 5.15. I'm hoping to land all the "compile time" stuff for 5.15, but realistically, some portions may not get there. I'll just carry this patch for now and if we need to swap trees we can do that. :) Thanks! -Kees -- Kees Cook