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=-19.1 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_GIT autolearn=unavailable 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 59447C49EA7 for ; Fri, 25 Jun 2021 07:37:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 46DAE6141E for ; Fri, 25 Jun 2021 07:37:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230037AbhFYHjq (ORCPT ); Fri, 25 Jun 2021 03:39:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230008AbhFYHjp (ORCPT ); Fri, 25 Jun 2021 03:39:45 -0400 Received: from mail-pj1-x1036.google.com (mail-pj1-x1036.google.com [IPv6:2607:f8b0:4864:20::1036]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B943C06175F for ; Fri, 25 Jun 2021 00:37:24 -0700 (PDT) Received: by mail-pj1-x1036.google.com with SMTP id bb10-20020a17090b008ab029016eef083425so7453416pjb.5 for ; Fri, 25 Jun 2021 00:37:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=LzgP6h2D/QFeac1VzX61noEzAJ/USmwi4gQaHInAahw=; b=LXB8g40vStNBwD+4feBv7G1sswWg7tKXE2UuAUSDoyq52hfi4irDQ/yiXu8Ug+ZDws xIzft/b25MjWvtHFPnJ6SklO93ihyo0nBxWHm/9AZX/s3potEvqVSuo/FGmincAfc25Y X1yk5o0729qjIfPuIaA+V96KO60J3W+vXFDLY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=LzgP6h2D/QFeac1VzX61noEzAJ/USmwi4gQaHInAahw=; b=bXgl/Hx4dBTb4PObaJTMqhTQoLoEoMFg8pgzd6J0pcnSwAZU8NmxH2DjSqBWgTFh/i tC3mvMO2vege8gFyJ2mE+5EwzNwD4/LzZzSUeaPjc+Im3iI3ZmuiTkhpEMzkH5q/ATEE IlcPcDqVMx3gzAjChRANTFcSc//rs5ZjPGWd5fGF09YcIt/s821yR49kBZqL782YAKR2 IQdXvDtlz7qz2vs3R3EPxmTqB+4WyIT4xcRJWcUS9jdIQ4LtyiVO5f540jvRpKjNliPm EE3yKdb7k1SzEziza2P7UuJFM5QP+Fx0OKEr20S5hX582Vp0nBE+3379/+avHq67zHhq fsrw== X-Gm-Message-State: AOAM533yC2oLUt62gEztvkAfvXw0a+dVJe+ZteW534Pfu2TIens46kT7 OBfADLcF1y2ciLEe8Syo4nJNCw== X-Google-Smtp-Source: ABdhPJzquQUc1a7oAEf0YGdzW5/tdcjfbVYUNDDWR+jVqhrRl2C1S/KaYW68U6E8tZbflFTo+iOEfA== X-Received: by 2002:a17:902:e843:b029:109:4dbc:d4ed with SMTP id t3-20020a170902e843b02901094dbcd4edmr7948926plg.74.1624606643957; Fri, 25 Jun 2021 00:37:23 -0700 (PDT) Received: from localhost ([2401:fa00:8f:203:1492:9d4f:19fa:df61]) by smtp.gmail.com with UTF8SMTPSA id r4sm4766830pja.41.2021.06.25.00.37.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Jun 2021 00:37:23 -0700 (PDT) From: David Stevens X-Google-Original-From: David Stevens To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Paolo Bonzini , Nick Piggin Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Will Deacon , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Zhenyu Wang , Zhi Wang , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH v2 1/5] KVM: do not allow mapping valid but non-refcounted pages Date: Fri, 25 Jun 2021 16:36:12 +0900 Message-Id: <20210625073616.2184426-2-stevensd@google.com> X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog In-Reply-To: <20210625073616.2184426-1-stevensd@google.com> References: <20210625073616.2184426-1-stevensd@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Nicholas Piggin It's possible to create a region which maps valid but non-refcounted pages (e.g., tail pages of non-compound higher order allocations). These host pages can then be returned by gfn_to_page, gfn_to_pfn, etc., family of APIs, which take a reference to the page, which takes it from 0 to 1. When the reference is dropped, this will free the page incorrectly. Fix this by only taking a reference on the page if it was non-zero, which indicates it is participating in normal refcounting (and can be released with put_page). Signed-off-by: Nicholas Piggin --- virt/kvm/kvm_main.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3dcc2abbfc60..f7445c3bcd90 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2175,6 +2175,13 @@ static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault) return true; } +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)); +} + static int hva_to_pfn_remapped(struct vm_area_struct *vma, unsigned long addr, bool *async, bool write_fault, bool *writable, @@ -2224,13 +2231,21 @@ static int hva_to_pfn_remapped(struct vm_area_struct *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. */ - kvm_get_pfn(pfn); + if (!kvm_try_get_pfn(pfn)) + r = -EFAULT; out: pte_unmap_unlock(ptep, ptl); *p_pfn = pfn; - return 0; + + return r; } /* -- 2.32.0.93.g670b81a890-goog