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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 90F5CC4360F for ; Thu, 4 Apr 2019 15:01:36 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 5B3FC2064A for ; Thu, 4 Apr 2019 15:01:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gsuVO3ZQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B3FC2064A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=TiOxINYTNPbcFzSpdZNBTJPJAuS0DYdRVD1tLTFELOA=; b=gsuVO3ZQ0fxfuc vZqXITPA/e2E33B887gGc63W9BoDuv1qR9iLT93u5ZO2/hogpdorOt6hRgfMDRzeYaNyVblHWZ6Kx p9OqD8GXeFWSGnqr58mAit/wxKc47FXW5E137eGmjf6tiBJU2xJRaacAOFqZfoLlpFjqRFlnQ2lBe z05uWq7kX2PLeyJlPYqSmY629XQ23aeIw049oA5i/PMFOau0j5+B+jaX+fisn2xfc8EBZqed2evlc E+pXa5mDywDeWt+gxJqs1tJWqhfTbXgLQorRPgsS2ZGEjbyB4sSp5DvXWOxauB1N7vIEIZeSW7ggU HV2oh+9I+zM58asN91HA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hC3rs-0005u5-3A; Thu, 04 Apr 2019 15:01:28 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hC3qj-0005Qt-0x for linux-arm-kernel@lists.infradead.org; Thu, 04 Apr 2019 15:00:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 809B9169E; Thu, 4 Apr 2019 08:00:16 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8F8753F59C; Thu, 4 Apr 2019 08:00:14 -0700 (PDT) Date: Thu, 4 Apr 2019 16:00:05 +0100 From: Will Deacon To: Douglas Anderson Subject: Re: [PATCH v2] iommu/arm-smmu: Break insecure users by disabling bypass by default Message-ID: <20190404145957.GA25912@fuggles.cambridge.arm.com> References: <20190301192017.39770-1-dianders@chromium.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190301192017.39770-1-dianders@chromium.org> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190404_080017_471074_11A8408B X-CRM114-Status: GOOD ( 19.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-msm@vger.kernel.org, Joerg Roedel , linux-kernel@vger.kernel.org, evgreen@chromium.org, tfiga@chromium.org, Rob Clark , iommu@lists.linux-foundation.org, Vivek Gautam , Robin Murphy , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Mar 01, 2019 at 11:20:17AM -0800, Douglas Anderson wrote: > If you're bisecting why your peripherals stopped working, it's > probably this CL. Specifically if you see this in your dmesg: > Unexpected global fault, this could be serious > ...then it's almost certainly this CL. > > Running your IOMMU-enabled peripherals with the IOMMU in bypass mode > is insecure and effectively disables the protection they provide. > There are few reasons to allow unmatched stream bypass, and even fewer > good ones. > > This patch starts the transition over to make it much harder to run > your system insecurely. Expected steps: > > 1. By default disable bypass (so anyone insecure will notice) but make > it easy for someone to re-enable bypass with just a KConfig change. > That's this patch. > > 2. After people have had a little time to come to grips with the fact > that they need to set their IOMMUs properly and have had time to > dig into how to do this, the KConfig will be eliminated and bypass > will simply be disabled. Folks who are truly upset and still > haven't fixed their system can either figure out how to add > 'arm-smmu.disable_bypass=n' to their command line or revert the > patch in their own private kernel. Of course these folks will be > less secure. > > Suggested-by: Robin Murphy > Signed-off-by: Douglas Anderson > --- > > Changes in v2: > - Flipped default to 'yes' and changed comments a lot. > > drivers/iommu/Kconfig | 25 +++++++++++++++++++++++++ > drivers/iommu/arm-smmu.c | 3 ++- > 2 files changed, 27 insertions(+), 1 deletion(-) Cheers, I'll pick this one up for 5.2. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel