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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 5933BC56202 for ; Wed, 4 Nov 2020 16:51:51 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 DB2D12087C for ; Wed, 4 Nov 2020 16:51:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sH57WiG8"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="C3pX6cmo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB2D12087C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.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: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:References:List-Owner; bh=CjaATYCctoqPTQlzKbZNfPApXVhGaRCGeww51rlJiqM=; b=sH57WiG85S6nOGQ+WspuekgdH d5vraVojf70+KZiPRZiVLD4akvX4I183t7+vAj1P95btHLcHc+dQxu8Tmi7dLMGgxd4wSR5nS3mnz OrkwIiqtm5WdOmIorjPERCI9GkZnCBz+LSP0bN+urAAeCFW5DNUi8tzYyDwSt/KU4IlD2G5F8H29m DZqqzgg5nCUVVVUm6jBy+hu4wvwivzG3+6iU/Yfkg0o97PpTemcuPlQXjWXaba156cPoObZSSE27P xCgnbYI5k690TpHuVMsSjSaR+fyTqFTJnPA1oDS+BgpcZ/dCN3mjMXjPN0LzoTa6FtWJIPLBDspYS k52T5GNlw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kaLzN-00086q-4S; Wed, 04 Nov 2020 16:50:25 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kaLzI-00085C-Kd for linux-arm-kernel@lists.infradead.org; Wed, 04 Nov 2020 16:50:21 +0000 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 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-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201104_115020_864661_9771EEEF X-CRM114-Status: GOOD ( 30.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-samsung-soc , Jan Kara , Kees Cook , KVM list , Jason Gunthorpe , John Hubbard , LKML , DRI Development , Linux MM , =?iso-8859-1?B?Suly9G1l?= Glisse , Linux PCI , Bjorn Helgaas , Daniel Vetter , Dan Williams , Andrew Morton , Linux ARM , "Linux-media@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel