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=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 A9E19C4320A for ; Tue, 24 Aug 2021 18:55:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90BD161374 for ; Tue, 24 Aug 2021 18:55:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233882AbhHXS4a (ORCPT ); Tue, 24 Aug 2021 14:56:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:54640 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230500AbhHXS41 (ORCPT ); Tue, 24 Aug 2021 14:56:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id DC45C61178; Tue, 24 Aug 2021 18:55:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629831343; bh=d/Fr0mBMXraTW+Ew01Yil+DCXSSjTvd5q9qem138RPE=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=t5cnqJZj36He9/zjegb9+V9+U3YiQamVwwKvzU1WrQq1Qaa+otNQjIpOiBqlsMEdM /Hqh3iR5wCXL+mGe6LqhWoGFpktgZ9b12IewTtcxFDv1maXi/yfljyIhDOnl/z5XMt kqtFzOpSSbjXME95XQ70DtnBwGzFO7+zGwLjQy9HFrGMtxqHJNh2QDgWLglZ5C35GH hnCcNOL4lw0MsGxbMWF0J/SLHbKZSnrBA1q8ych11j+zeKHwRGuUnfE1N3/f5XMPXs oyQMr/mk68NjLI3llarex6W2QR/Y9G8ODdkhohBntXV7QiObuNljxc6qSrgPHYc8ep rrO89m1YOIQlQ== Date: Tue, 24 Aug 2021 13:55:41 -0500 From: Bjorn Helgaas To: Andi Kleen Cc: "Michael S. Tsirkin" , Dan Williams , "Kuppuswamy, Sathyanarayanan" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Bjorn Helgaas , Richard Henderson , Thomas Bogendoerfer , James E J Bottomley , Helge Deller , "David S . Miller" , Arnd Bergmann , Jonathan Corbet , Peter H Anvin , Dave Hansen , Tony Luck , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , X86 ML , Linux Kernel Mailing List , Linux PCI , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch , Linux Doc Mailing List , virtualization@lists.linux-foundation.org, Rajat Jain Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range} Message-ID: <20210824185541.GA3485816@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org [+cc Rajat; I still don't know what "shared memory with a hypervisor in a confidential guest" means, but now we're talking about hardened drivers and allow lists, which Rajat is interested in] On Tue, Aug 24, 2021 at 10:20:44AM -0700, Andi Kleen wrote: > > > I see. Hmm. It's a bit of a random thing to do it at the map time > > though. E.g. DMA is all handled transparently behind the DMA API. > > Hardening is much more than just replacing map with map_shared > > and I suspect what you will end up with is basically > > vendors replacing map with map shared to make things work > > for their users and washing their hands. > > That concept exists too. There is a separate allow list for the drivers. So > just adding shared to a driver is not enough, until it's also added to the > allowlist > > Users can of course chose to disable the allowlist, but they need to > understand the security implications. > > > I would say an explicit flag in the driver that says "hardened" > > and refusing to init a non hardened one would be better. > > We have that too (that's the device filtering) > > But the problem is that device filtering just stops the probe functions, not > the initcalls, and lot of legacy drivers do MMIO interactions before going > into probe. In some cases it's unavoidable because of the device doesn't > have a separate enumeration mechanism it needs some kind of probing to even > check for its existence And since we don't want to change all of them it's > far safer to make the ioremap opt-in. > > > -Andi >