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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS autolearn=ham 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 D3332C282C8 for ; Mon, 28 Jan 2019 19:00:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A134E20989 for ; Mon, 28 Jan 2019 19:00:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="kfKH+nma" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727225AbfA1TAc (ORCPT ); Mon, 28 Jan 2019 14:00:32 -0500 Received: from mail-vk1-f194.google.com ([209.85.221.194]:37958 "EHLO mail-vk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726678AbfA1TAb (ORCPT ); Mon, 28 Jan 2019 14:00:31 -0500 Received: by mail-vk1-f194.google.com with SMTP id w72so3914469vkd.5 for ; Mon, 28 Jan 2019 11:00:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=HW28ls7Wx+igmjl+yu70fqcBEBBFWWC4XR6jh21UZYg=; b=kfKH+nmaemVN1YLHaFgCdpR8oIM1Il/wC44Xsc3dCbL7K7GWHY/x23uRnB+zY2JwO9 0goxzN28D1fXTVU7AgBKBinIv1rd824L7tNtIe/DlAN6O4P8Sil7cwq77F0jP6G83wJ7 6/t4SE/k8w1Hl1+2IJGM1jRzyCkgua/nCMkPQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=HW28ls7Wx+igmjl+yu70fqcBEBBFWWC4XR6jh21UZYg=; b=gC23AxRXPcF+lkbzEDk7GdRIo1jQIEqu69jxvuXB/4ewcVpK7Dg6F3fBEMXVZuFoi1 BTf671U1HAYTWqYHet5RpYMXovVAEDkOzcBNx/+LXAHYt56a7s7fBVb7WeUyG+KcdAJR ySgJsqC1OsEuzYDjX8A7HViShsCXwAZhsEsmHAxzfpxHJHpG7BdKkUJdl7kdRJNn3CPn 8YMnEGk75R3yhcPAkZVg892T1cPiLDtwMshhfU5kteW0l2sHAEkJRRBujCRX4D4RzH8C lI2mQTSNo7HfNHsZOaoTr7YlgdeDHXOaASBhM0I+EpSGbvf7ETUQMhSYpsZNIu6eAnYa gigQ== X-Gm-Message-State: AJcUukf1wJBdp0c2Hv/PRT3HDteLaEYPpVLh0ecv4wyKCtFj4Lt3mUn+ vXm9Y8IrpsaAbbDJ/x/Eh/Z8jozpwcc= X-Google-Smtp-Source: ALg8bN7F4r3zsttfF3aFXO3YOSO/dLOfZrLFVcC1OLwG16JPdZSOidSpl0eZsq7lYBf12BnlMCnbUA== X-Received: by 2002:a1f:2d89:: with SMTP id t131mr8843622vkt.27.1548702030160; Mon, 28 Jan 2019 11:00:30 -0800 (PST) Received: from mail-ua1-f52.google.com (mail-ua1-f52.google.com. [209.85.222.52]) by smtp.gmail.com with ESMTPSA id t133sm35056961vsc.8.2019.01.28.11.00.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 11:00:27 -0800 (PST) Received: by mail-ua1-f52.google.com with SMTP id t8so6002853uap.0 for ; Mon, 28 Jan 2019 11:00:26 -0800 (PST) X-Received: by 2002:ab0:740a:: with SMTP id r10mr9002232uap.14.1548702026118; Mon, 28 Jan 2019 11:00:26 -0800 (PST) MIME-Version: 1.0 References: <20190125173827.2658-1-willy@infradead.org> <20190128102055.5b0790549542891c4dca47a3@linux-foundation.org> In-Reply-To: <20190128102055.5b0790549542891c4dca47a3@linux-foundation.org> From: Kees Cook Date: Tue, 29 Jan 2019 08:00:14 +1300 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm: Prevent mapping slab pages to userspace To: Andrew Morton Cc: Matthew Wilcox , Linux-MM , LKML , Rik van Riel , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Kernel Hardening , Michael Ellerman Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 29, 2019 at 7:21 AM Andrew Morton wrote: > > On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox wrote: > > > It's never appropriate to map a page allocated by SLAB into userspace. > > A buggy device driver might try this, or an attacker might be able to > > find a way to make it happen. > > It wouldn't surprise me if someone somewhere is doing this. Rather > than mysteriously breaking their code, how about we emit a warning and > still permit it to proceed, for a while? It seems like a fatal condition to me? There's nothing to check that such a page wouldn't get freed by the slab while still mapped to userspace, right? But I'll take warning over not checking. :) -- Kees Cook 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=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS 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 32328C282CF for ; Mon, 28 Jan 2019 19:00:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C75AA21741 for ; Mon, 28 Jan 2019 19:00:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="kfKH+nma" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C75AA21741 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 100E08E0002; Mon, 28 Jan 2019 14:00:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 088E38E0001; Mon, 28 Jan 2019 14:00:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EE1C38E0002; Mon, 28 Jan 2019 14:00:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-vk1-f199.google.com (mail-vk1-f199.google.com [209.85.221.199]) by kanga.kvack.org (Postfix) with ESMTP id BE39F8E0001 for ; Mon, 28 Jan 2019 14:00:32 -0500 (EST) Received: by mail-vk1-f199.google.com with SMTP id s196so4683829vke.7 for ; Mon, 28 Jan 2019 11:00:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:mime-version:references :in-reply-to:from:date:message-id:subject:to:cc; bh=HW28ls7Wx+igmjl+yu70fqcBEBBFWWC4XR6jh21UZYg=; b=fzrzCNDEBmPLGrkaQj2od5ewRyXK2AV9ViI8lE42WtVKEPs7qJvXXl3eEtgkpVKjGF N3yqOoPqM6umIy0CjjKmxbPA0yqEdBZ44OjJHDcWNpCFl/kvP9B3rrUw8uIuv46aHVSr z03oqPlYwG+Wx5WFxHHf5KKkLne35h4NFU5LZ0kpnVnPvHhIY3owWltKtWzusycX8NL/ WVXVTRavjCtcG1LtDWeqUQQrx+QH3xU+awyk/op4pY2XRM/cKYMhsrYgnS4aEsp/8K7k M4zZOJbKpUAjxkI+UlkXwgi97ayVGKV6Mi/SoCQpmMnMKM69cLhGJINjCk57Z30LE5q6 kfkQ== X-Gm-Message-State: AJcUukdMAAnR0Af/KefO0+XC8YsDrivNlaypOlHTucsNsausnaLLtQ2R YWeDcfs7n527gu4/iAKVI0rUrsd4Nq004wljuFV2bjpRSa9lJaKT585UH3bQfFBaywkBbw+Xfu3 s7lU3gdxTPLJMcaE374vJVKkQ2BF8xTZzxVZG2zXdPVXN/ls87eLqX9IQFBMKCqQb52Fdm9De45 ZWdAt/QUFqQNRDn+wFpTFTWwxcDr9XavD01OWBxXtXS5TavkfVVMxSK7KNy/3755M32DPH8k6b5 etV2vNIQipvgCCDwYFzcgGhBPKEKh+6VRNgFhE7hY0+zIc/ZFtpNyWXlGTv+yxY0NKFq1oXH9jY Yi76rENUZcQQlZBFk0PQBsx8n0JSC+uQIm8zyHwFm5V7ARtsDRYvhPpwgZdyC/giQ+y05IqLdU7 + X-Received: by 2002:ab0:148e:: with SMTP id d14mr9406543uae.23.1548702032347; Mon, 28 Jan 2019 11:00:32 -0800 (PST) X-Received: by 2002:ab0:148e:: with SMTP id d14mr9406510uae.23.1548702031585; Mon, 28 Jan 2019 11:00:31 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1548702031; cv=none; d=google.com; s=arc-20160816; b=eo6E/NQ62NRk6KlRqEEdSCXYrV+KpA4KLjtsl66ofkdq844p+Z3fTVbKoE8IlpoKX9 yajIkXqdUlgdMrrsdDjq+PcljlIuPlx7SqB6EY6RuW9c9R8WBjroj8DtLcJJ2T3d0ldu RFXCUV+l36234ivemfPEn4VBAtHqTuKUznw7l7ocV3CzWTGxqMVUHp4+sVJ7uO47XN/j zjzUUGqC+EkRBPvltjsqef5saRgxd1Tb6TdthxFbSLpQayaQ71MU+aBQUipeNv+Zh3hk MnXOCMujCU3bJHzwQaBgNPKnsfkd8FU9fy2QQ4+VclMpjxJehRC2sggoTb4Hi9Yy7CpT ApcQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:dkim-signature; bh=HW28ls7Wx+igmjl+yu70fqcBEBBFWWC4XR6jh21UZYg=; b=YYFuTsEZy9iPIsB/odxfmAeuINTGfXiMVuhe2uleTTQBoC3aOu2NUXuGa+Ofwk+7BE ZK8SjAUNtG08HdS7ddGCkAggAKb15FqmNqgZRVBMgS1p3D9g8QRDZtbcBprtcmSmkJYC Nsvq4v3Jr4HUXJ4TlotAC8zA7NMHMjqBxBtdbo1w4/ze7VECm9kfKQdkaC0scURMTibh v4EBasDNvBmiigHUPwL7pf+CqQGMzmD/VFuBn4yp/VNPR8JWR1+eUNQvI780Lshh4kNT tyGg9uM+/DUIFcdOxgrZ9RhyNngMVrOcrkaXwYJMbNIlRLyCgKAku7bkHJ5RBq9Ro9Ng tQIg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=kfKH+nma; spf=pass (google.com: domain of keescook@chromium.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. 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[209.85.222.51]) by smtp.gmail.com with ESMTPSA id k200sm74658399vke.9.2019.01.28.11.00.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 11:00:28 -0800 (PST) Received: by mail-ua1-f51.google.com with SMTP id d19so5989509uaq.11 for ; Mon, 28 Jan 2019 11:00:26 -0800 (PST) X-Received: by 2002:ab0:740a:: with SMTP id r10mr9002232uap.14.1548702026118; Mon, 28 Jan 2019 11:00:26 -0800 (PST) MIME-Version: 1.0 References: <20190125173827.2658-1-willy@infradead.org> <20190128102055.5b0790549542891c4dca47a3@linux-foundation.org> In-Reply-To: <20190128102055.5b0790549542891c4dca47a3@linux-foundation.org> From: Kees Cook Date: Tue, 29 Jan 2019 08:00:14 +1300 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm: Prevent mapping slab pages to userspace To: Andrew Morton Cc: Matthew Wilcox , Linux-MM , LKML , Rik van Riel , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Kernel Hardening , Michael Ellerman Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 29, 2019 at 7:21 AM Andrew Morton wrote: > > On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox wrote: > > > It's never appropriate to map a page allocated by SLAB into userspace. > > A buggy device driver might try this, or an attacker might be able to > > find a way to make it happen. > > It wouldn't surprise me if someone somewhere is doing this. Rather > than mysteriously breaking their code, how about we emit a warning and > still permit it to proceed, for a while? It seems like a fatal condition to me? There's nothing to check that such a page wouldn't get freed by the slab while still mapped to userspace, right? But I'll take warning over not checking. :) -- Kees Cook