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=-5.5 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 DB832C48BDF for ; Thu, 24 Jun 2021 10:35:14 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 865DE613F0 for ; Thu, 24 Jun 2021 10:35:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 865DE613F0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4G9c360Zjqz3c68 for ; Thu, 24 Jun 2021 20:35:14 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=ItVpaR72; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gmail.com (client-ip=2607:f8b0:4864:20::1029; helo=mail-pj1-x1029.google.com; envelope-from=npiggin@gmail.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=ItVpaR72; dkim-atps=neutral Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4G9c2P1D1Zz3bxW for ; Thu, 24 Jun 2021 20:34:36 +1000 (AEST) Received: by mail-pj1-x1029.google.com with SMTP id p4-20020a17090a9304b029016f3020d867so3196108pjo.3 for ; Thu, 24 Jun 2021 03:34:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :message-id:content-transfer-encoding; bh=ISlLS/Bnqpf/oAWEGOJgKBZ0Rb18u3bU0Ep0kv2LMg0=; b=ItVpaR72A3eWg+6QNdd9RNw76aFcKOXvgi86A4U+ygjRobuSVtqGLn83lJQMbfCPA4 LQIa3P9bWqZxWn65q97p0mTXZfMJxza4XBkddIpoDzA0Y1gz2b4OTCDChEW1fNnXNMtx Fd/HR/h+M9YqDeioWNf5AArKjGRkQ+rrWucptSeSf/UUf6QUwL4Nowo/4rEimVbdxS4Q CrrkCNn+4rsxvoMWh2fX66Avx4PzjnR2opDju0qKu/sbanWcGLqwESvvdl5Yw6PwyCya zQM4h5g6tjIbnWhNNgTE1fjofoOSBjtXdTRyzTMD0NSsHlc5YkGJ7hehN9KlI5q5bxjS Pecg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:message-id:content-transfer-encoding; bh=ISlLS/Bnqpf/oAWEGOJgKBZ0Rb18u3bU0Ep0kv2LMg0=; b=X+cxMs8XkH8M620Xa8tt+CgYX0PfeOknXpqWWIBi/SzqMqBkmkDt3vnOg6rTZJc3f6 oDn4/gnG/GhoStjWgx/6UQNoyRj8Y12uGM6Xh9tU7wyBteXh7z4lNLSDwp23UIdR/dKy LBtK107oMp4TOQYKQjvz7R0d8Vu2mGNhBvzHW3Cx4Zc/80qLEQjeqXahcsLG2J7gm50t O9ngZ8W6MUOZ08dP27wk2LMjox3MBBlWyTd90QkfQBNrbTMe+Cx8s6x8Q30FIGtm6ZzP 11eDtfZI4JkFSUudP7RmnIK4NIEDylN10MIIF9c74VDtNOBsASIRTIJd5VuZZTIECdlN Qpww== X-Gm-Message-State: AOAM530apY7cPRUkh6lMevFPbupnWLXOmvrbsbupoKPVah9zvPYc60u/ cvrhCp6hyCHxfvlCOPdKcwM= X-Google-Smtp-Source: ABdhPJy6kajrzF0OadUDC6nHAS6U7gmSDYSh4DBdORcOqITOBjGnDhRDrYwGVGZv+udz0pGSetXg8w== X-Received: by 2002:a17:90b:4ac6:: with SMTP id mh6mr15043416pjb.210.1624530871905; Thu, 24 Jun 2021 03:34:31 -0700 (PDT) Received: from localhost (60-242-147-73.tpgi.com.au. [60.242.147.73]) by smtp.gmail.com with ESMTPSA id k63sm7664839pjh.13.2021.06.24.03.34.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Jun 2021 03:34:31 -0700 (PDT) Date: Thu, 24 Jun 2021 20:34:25 +1000 From: Nicholas Piggin Subject: Re: [PATCH 0/6] KVM: Remove uses of struct page from x86 and arm64 MMU To: Aleksandar Markovic , Huacai Chen , Marc Zyngier , Paul Mackerras , Paolo Bonzini , David Stevens , Zhenyu Wang , Zhi Wang References: <20210624035749.4054934-1-stevensd@google.com> In-Reply-To: <20210624035749.4054934-1-stevensd@google.com> MIME-Version: 1.0 Message-Id: <1624530624.8jff1f4u11.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Wanpeng Li , kvm@vger.kernel.org, David Stevens , Alexandru Elisei , intel-gfx@lists.freedesktop.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, kvmarm@lists.cs.columbia.edu, Will Deacon , Suzuki K Poulose , James Morse , kvm-ppc@vger.kernel.org, Sean Christopherson , Vitaly Kuznetsov , linux-mips@vger.kernel.org, intel-gvt-dev@lists.freedesktop.org, Joerg Roedel , linux-arm-kernel@lists.infradead.org, Jim Mattson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from David Stevens's message of June 24, 2021 1:57 pm: > KVM supports mapping VM_IO and VM_PFNMAP memory into the guest by using > follow_pte in gfn_to_pfn. However, the resolved pfns may not have > assoicated struct pages, so they should not be passed to pfn_to_page. > This series removes such calls from the x86 and arm64 secondary MMU. To > do this, this series modifies gfn_to_pfn to return a struct page in > addition to a pfn, if the hva was resolved by gup. This allows the > caller to call put_page only when necessated by gup. >=20 > This series provides a helper function that unwraps the new return type > of gfn_to_pfn to provide behavior identical to the old behavior. As I > have no hardware to test powerpc/mips changes, the function is used > there for minimally invasive changes. Additionally, as gfn_to_page and > gfn_to_pfn_cache are not integrated with mmu notifier, they cannot be > easily changed over to only use pfns. >=20 > This addresses CVE-2021-22543 on x86 and arm64. Does this fix the problem? (untested I don't have a POC setup at hand, but at least in concept) I have no problem with improving the API and probably in the direction=20 of your series is good. But there seems to be a lot of unfixed arch code=20 and broken APIs remaining left to do after your series too. This might=20 be most suitable to backport and as a base for your series that can take more time to convert to new APIs. Thanks, Nick --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6a6bc7af0e28..e208c279d903 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2104,13 +2104,21 @@ static int hva_to_pfn_remapped(struct vm_area_struc= t *vma, * Whoever called remap_pfn_range is also going to call e.g. * unmap_mapping_range before the underlying pages are freed, * causing a call to our MMU notifier. + * + * Certain IO or PFNMAP mappings can be backed with valid + * struct pages, but be allocated without refcounting e.g., + * tail pages of non-compound higher order allocations, which + * would then underflow the refcount when the caller does the + * required put_page. Don't allow those pages here. */=20 - kvm_get_pfn(pfn); + if (!kvm_try_get_pfn(pfn)) + r =3D -EFAULT; =20 out: pte_unmap_unlock(ptep, ptl); *p_pfn =3D pfn; - return 0; + + return r; } =20 /* @@ -2487,6 +2495,13 @@ void kvm_set_pfn_accessed(kvm_pfn_t pfn) } EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed); =20 +static int kvm_try_get_pfn(kvm_pfn_t pfn) +{ + if (kvm_is_reserved_pfn(pfn)) + return 1; + return get_page_unless_zero(pfn_to_page(pfn)); +} + void kvm_get_pfn(kvm_pfn_t pfn) { if (!kvm_is_reserved_pfn(pfn))