Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935333AbdDFOpw (ORCPT ); Thu, 6 Apr 2017 10:45:52 -0400 Received: from foss.arm.com ([217.140.101.70]:44216 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755664AbdDFOpo (ORCPT ); Thu, 6 Apr 2017 10:45:44 -0400 Subject: Re: [PATCH V10 06/12] of: device: Fix overflow of coherent_dma_mask To: Rob Herring References: <1489086061-9356-1-git-send-email-sricharan@codeaurora.org> <1491301105-5274-1-git-send-email-sricharan@codeaurora.org> <1491301105-5274-7-git-send-email-sricharan@codeaurora.org> <58E5E7B7.1050400@gmail.com> Cc: Frank Rowand , Sricharan R , Will Deacon , Joerg Roedel , Lorenzo Pieralisi , Linux IOMMU , "linux-arm-kernel@lists.infradead.org" , linux-arm-msm , Marek Szyprowski , "bhelgaas@google.com" , "linux-pci@vger.kernel.org" , "linux-acpi@vger.kernel.org" , Tomasz Nowicki , Hanjun Guo , Sinan Kaya , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Sudeep Holla , "Rafael J. Wysocki" , Len Brown , Catalin Marinas , Arnd Bergmann , "linux-arch@vger.kernel.org" , Greg Kroah-Hartman From: Robin Murphy Message-ID: Date: Thu, 6 Apr 2017 15:45:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2860 Lines: 67 On 06/04/17 14:56, Rob Herring wrote: > On Thu, Apr 6, 2017 at 5:24 AM, Robin Murphy wrote: >> On 06/04/17 08:01, Frank Rowand wrote: >>> On 04/04/17 03:18, Sricharan R wrote: >>>> Size of the dma-range is calculated as coherent_dma_mask + 1 >>>> and passed to arch_setup_dma_ops further. It overflows when >>>> the coherent_dma_mask is set for full 64 bits 0xFFFFFFFFFFFFFFFF, >>>> resulting in size getting passed as 0 wrongly. Fix this by >>>> passsing in max(mask, mask + 1). Note that in this case >>>> when the mask is set to full 64bits, we will be passing the mask >>>> itself to arch_setup_dma_ops instead of the size. The real fix >>>> for this should be to make arch_setup_dma_ops receive the >>>> mask and handle it, to be done in the future. >>>> >>>> Signed-off-by: Sricharan R >>>> --- >>>> drivers/of/device.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/device.c b/drivers/of/device.c >>>> index c17c19d..c2ae6bb 100644 >>>> --- a/drivers/of/device.c >>>> +++ b/drivers/of/device.c >>>> @@ -107,7 +107,7 @@ void of_dma_configure(struct device *dev, struct device_node *np) >>>> ret = of_dma_get_range(np, &dma_addr, &paddr, &size); >>>> if (ret < 0) { >>>> dma_addr = offset = 0; >>>> - size = dev->coherent_dma_mask + 1; >>>> + size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1); >>>> } else { >>>> offset = PFN_DOWN(paddr - dma_addr); >>>> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >>>> >>> >>> NACK. >>> >>> Passing an invalid size to arch_setup_dma_ops() is only part of the problem. >>> size is also used in of_dma_configure() before calling arch_setup_dma_ops(): >>> >>> dev->coherent_dma_mask = min(dev->coherent_dma_mask, >>> DMA_BIT_MASK(ilog2(dma_addr + size))); >>> *dev->dma_mask = min((*dev->dma_mask), >>> DMA_BIT_MASK(ilog2(dma_addr + size))); >>> >>> which would be incorrect for size == 0xffffffffffffffffULL when >>> dma_addr != 0. So the proposed fix really is not papering over >>> the base problem very well. >> >> I'm not sure I agree there. Granted, there exist many more problematic >> aspects than are dealt with here (I've got more patches cooking to sort >> out some of the other issues we have with dma-ranges), but considering >> size specifically: >> >> - It is not possible to explicitly specify a range with a size of 2^64 >> in DT. If someone does specify a size of 0, they've done a silly thing >> and should not be surprised that it ends badly. > > And because of this, we allow ~0 (both 32 and 64 bit) in DT dma-ranges > and fix these up as 2^32 and 2^64 sizes. ...which is what Frank's patch gets rid of. Robin. > > Rob >