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 A26DAC433F5 for ; Fri, 18 Feb 2022 17:17:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234604AbiBRRRn (ORCPT ); Fri, 18 Feb 2022 12:17:43 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:45104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238344AbiBRRPr (ORCPT ); Fri, 18 Feb 2022 12:15:47 -0500 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 030E32B5230 for ; Fri, 18 Feb 2022 09:15:27 -0800 (PST) Received: by mail-pj1-x102b.google.com with SMTP id a11-20020a17090a740b00b001b8b506c42fso12976635pjg.0 for ; Fri, 18 Feb 2022 09:15:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=5DBNroUKPfQERghwahUfBWjvAkNxMqGLB1PH+8DKuNc=; b=sHg3ObPWzkeC9xEO0V7DReNTB+4arPdrOPPDTmavWb5B9DZkREfKPq+3FpWBa403Lw Y5t53RaSluKTmLmNHRyur9hYMmHAGLgLMMAI9ZZbiNy8UlIbW/ZGkYCdPgABD0AC2T9u wKWYtt0XeXFY2WfwMfoSkvlcdhLyHj997+0tCVf6DE+moJBJXVSuJPlhu9L6zFceEp+Y hfaDc1XmVEbolMObbXCG6QURvbRe+kHph+8PAKn1JulfgmdoCvc2Ohn3pIQm1ymvmIn+ 13SIsdwC8zCLIm2zZwwsnzRC2s0H8azX8RkjbmF9uEIa/dkiSNanBcJyBfZMtoNe3gS/ xzLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5DBNroUKPfQERghwahUfBWjvAkNxMqGLB1PH+8DKuNc=; b=oWIvzhmeL1hhKux0Vrz5m2KmNxA9e+UEp6elN+kA5j4gnSImLO9iMsJ5ejzEVMbbfo RaMpWsdwoCXwoFGN8uxaPI8C1j886hXOsJ+aE5y50NrgdOtU3NRhoqlm6VcG/E7UlvBp KOh1eS+ocT6yaZKT0Qae4Ic768k7iAFVG2MIO/F/LL8e6wGNwrgRXm+r9xYS3PuVsxRc 0R4MT7ltA07w71qDooFqr7AJyaC+jiFlCCoEyJgEe/X+5lwRA2T5yOdy6fOmmFSf282o WyjDw0zauX+cfiPq13/RwhyXKrBv4IjBZ//cm0reJAZPK28uNo5z28JQd0fLKr7xep0Y Noyg== X-Gm-Message-State: AOAM530Gmkqy3MxkZRwd2zvEaLbLhevs18N8SJbCrviBOw6Ls+G3vB+m l8FTiUqV64euJTensPFm5VIbxw== X-Google-Smtp-Source: ABdhPJzlvWoSjWwc9M5oN1R7z8trnYPRzDDfCSzYbcFXbOyMmf/dsym7BNfiUqYWis5pQSn1bh/9ww== X-Received: by 2002:a17:90a:6809:b0:1b9:bc46:fdd7 with SMTP id p9-20020a17090a680900b001b9bc46fdd7mr13616473pjj.148.1645204526362; Fri, 18 Feb 2022 09:15:26 -0800 (PST) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id gm6-20020a17090b100600b001b8b502d18bsm6838pjb.19.2022.02.18.09.15.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Feb 2022 09:15:25 -0800 (PST) Date: Fri, 18 Feb 2022 17:15:22 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v2 04/18] KVM: x86/mmu: avoid NULL-pointer dereference on page freeing bugs Message-ID: References: <20220217210340.312449-1-pbonzini@redhat.com> <20220217210340.312449-5-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220217210340.312449-5-pbonzini@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 17, 2022, Paolo Bonzini wrote: > WARN and bail if KVM attempts to free a root that isn't backed by a shadow > page. KVM allocates a bare page for "special" roots, e.g. when using PAE > paging or shadowing 2/3/4-level page tables with 4/5-level, and so root_hpa > will be valid but won't be backed by a shadow page. It's all too easy to > blindly call mmu_free_root_page() on root_hpa, be nice and WARN instead of > crashing KVM and possibly the kernel. > > Signed-off-by: Paolo Bonzini > --- Reviewed-by: Sean Christopherson