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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D808FC4742C for ; Wed, 4 Nov 2020 16:51:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88DEC206E3 for ; Wed, 4 Nov 2020 16:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604508698; bh=KzXcQsv6oXQiPT6pQbTFR35Ks2A09AmGg4NdOMxDZU4=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=tJWp6hc/SjsqQNaCBGfgzrfSqGgUOOFAg7HbkV/ZNdPMZp+Tf51ocN/NoU4r+Ef0f iGOj09Ukr3fzn91U8GXi1wG9taAw4gaPO2tcpMJw1IhpsuVnAJnnhmNO06Vw91cu/z 96R4ky5C+r404oejubGCXYvuTjzxbyVXOS3Nhqq8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731836AbgKDQvf (ORCPT ); Wed, 4 Nov 2020 11:51:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:47120 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731683AbgKDQuU (ORCPT ); Wed, 4 Nov 2020 11:50:20 -0500 Received: from localhost (230.sub-72-107-127.myvzw.com [72.107.127.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 01712206CA; Wed, 4 Nov 2020 16:50:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604508619; bh=KzXcQsv6oXQiPT6pQbTFR35Ks2A09AmGg4NdOMxDZU4=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=C3pX6cmo6q8mwyEj5GO30o1K3DmrMhjsd197OHFiySwAIRZVIm3gcmWDrE+eCPQYz sPh4rcY/+zTADvqe8t10fQKgN6B/uva7r/Rm33jjbBhTlqD9gCI3SGCFFhZSFec0de QvdkQtLCYpZ8r9E77lkRpGYf+6s0+xBDMYsFK0NQ= Date: Wed, 4 Nov 2020 10:50:17 -0600 From: Bjorn Helgaas To: Daniel Vetter Cc: Dan Williams , DRI Development , LKML , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "Linux-media@vger.kernel.org" , Daniel Vetter , Jason Gunthorpe , Kees Cook , Andrew Morton , John Hubbard , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , Bjorn Helgaas , Linux PCI Subject: Re: [PATCH v5 11/15] PCI: Obey iomem restrictions for procfs mmap Message-ID: <20201104165017.GA352206@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-pci@vger.kernel.org On Wed, Nov 04, 2020 at 09:44:04AM +0100, Daniel Vetter wrote: > On Tue, Nov 3, 2020 at 11:09 PM Dan Williams wrote: > > On Tue, Nov 3, 2020 at 1:28 PM Bjorn Helgaas wrote: > > > On Fri, Oct 30, 2020 at 11:08:11AM +0100, Daniel Vetter wrote: > > > > There's three ways to access PCI BARs from userspace: /dev/mem, sysfs > > > > files, and the old proc interface. Two check against > > > > iomem_is_exclusive, proc never did. And with CONFIG_IO_STRICT_DEVMEM, > > > > this starts to matter, since we don't want random userspace having > > > > access to PCI BARs while a driver is loaded and using it. > > > > > > > > Fix this by adding the same iomem_is_exclusive() check we already have > > > > on the sysfs side in pci_mmap_resource(). > > > > > > > > References: 90a545e98126 ("restrict /dev/mem to idle io memory ranges") > > > > Signed-off-by: Daniel Vetter > > > > > > This is OK with me but it looks like IORESOURCE_EXCLUSIVE is currently > > > only used in a few places: > > > > > > e1000_probe() calls pci_request_selected_regions_exclusive(), > > > ne_pci_probe() calls pci_request_regions_exclusive(), > > > vmbus_allocate_mmio() calls request_mem_region_exclusive() > > > > > > which raises the question of whether it's worth keeping > > > IORESOURCE_EXCLUSIVE at all. I'm totally fine with removing it > > > completely. > > > > Now that CONFIG_IO_STRICT_DEVMEM upgrades IORESOURCE_BUSY to > > IORESOURCE_EXCLUSIVE semantics the latter has lost its meaning so I'd > > be in favor of removing it as well. > > Still has some value since it enforces exclusive access even if the > config isn't enabled, and iirc e1000 had some fun with userspace tools > clobbering the firmware and bricking the chip. There's *some* value; I'm just skeptical since only three drivers use it. IORESOURCE_EXCLUSIVE is from e8de1481fd71 ("resource: allow MMIO exclusivity for device drivers"), and the commit message says this is only active when CONFIG_STRICT_DEVMEM is set. I didn't check to see whether that's still true. That commit adds a bunch of wrappers and "__"-prefixed functions to pass the IORESOURCE_EXCLUSIVE flag around. That's a fair bit of uglification for three drivers. > Another thing I kinda wondered, since pci maintainer is here: At least > in drivers/gpu I see very few drivers explicitly requestion regions > (this might be a historical artifact due to the shadow attach stuff > before we had real modesetting drivers). And pci core doesn't do that > either, even when a driver is bound. Is this intentional, or > should/could we do better? Since drivers work happily without > reserving regions I don't think "the drivers need to remember to do > this" will ever really work out well. You're right, many drivers don't call pci_request_regions(). Maybe we could do better, but I haven't looked into that recently. There is a related note in Documentation/PCI/pci.rst that's been there for a long time (it refers to "pci_request_resources()", which has never existed AFAICT). I'm certainly open to proposals.