Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934895AbdDFN5Q (ORCPT ); Thu, 6 Apr 2017 09:57:16 -0400 Received: from mail.kernel.org ([198.145.29.136]:34338 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934909AbdDFN5B (ORCPT ); Thu, 6 Apr 2017 09:57:01 -0400 MIME-Version: 1.0 In-Reply-To: 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> From: Rob Herring Date: Thu, 6 Apr 2017 08:56:33 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH V10 06/12] of: device: Fix overflow of coherent_dma_mask To: Robin Murphy 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 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2699 Lines: 60 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. Rob