Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752166AbdFMJDd (ORCPT ); Tue, 13 Jun 2017 05:03:33 -0400 Received: from foss.arm.com ([217.140.101.70]:44732 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751753AbdFMJDc (ORCPT ); Tue, 13 Jun 2017 05:03:32 -0400 Date: Tue, 13 Jun 2017 10:03:28 +0100 From: Catalin Marinas To: Olav Haugan Cc: robin.murphy@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64/dma-mapping: Fix null-pointer check Message-ID: <20170613090328.GA3302@e104818-lin.cambridge.arm.com> References: <20170610194110.27712-1-ohaugan@codeaurora.org> <20170612122903.GC24187@e104818-lin.cambridge.arm.com> <20170612205028.y7a652hd46dakxdu@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170612205028.y7a652hd46dakxdu@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1631 Lines: 42 On Mon, Jun 12, 2017 at 01:50:28PM -0700, Olav Haugan wrote: > On 17-06-12 13:29:04, Catalin Marinas wrote: > > On Sat, Jun 10, 2017 at 12:41:10PM -0700, Olav Haugan wrote: > > > @@ -149,6 +140,11 @@ static void *__dma_alloc(struct device *dev, size_t size, > > > bool coherent = is_device_dma_coherent(dev); > > > pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL, false); > > > > > > + if (!dev) { > > > + WARN_ONCE(1, "Use an actual device structure for DMA allocation\n"); > > > + return NULL; > > > + } > > > + > > > size = PAGE_ALIGN(size); > > > > > > if (!coherent && !gfpflags_allow_blocking(flags)) { > > > @@ -192,8 +188,13 @@ static void __dma_free(struct device *dev, size_t size, > > > void *vaddr, dma_addr_t dma_handle, > > > unsigned long attrs) > > > { > > > - void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle)); > > > + void *swiotlb_addr; > > > > > > + if (!dev) { > > > + WARN_ONCE(1, "Use an actual device structure for DMA free\n"); > > > + return; > > > + } > > > + swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle)); > > > > I don't think we need the checks anymore. With commit 1dccb598df54 > > ("arm64: simplify dma_get_ops") __generic_dma_ops() returns > > dummy_dma_ops when dev == NULL, so the above __dma_alloc/__dma_free > > functions would not be called. > > We don't need the check in is_device_dma_coherent() either then right? Right. The only user of this function outside arch/arm64/mm/dma-mapping.c is Xen (shared with arm32 under arch/arm/xen/) but since arm32 doesn't do this NULL check either, we should be fine. -- Catalin