From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1948627AbcBSOGU (ORCPT ); Fri, 19 Feb 2016 09:06:20 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:34844 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946215AbcBSOGT (ORCPT ); Fri, 19 Feb 2016 09:06:19 -0500 Date: Fri, 19 Feb 2016 14:06:00 +0000 From: Russell King - ARM Linux To: Rabin Vincent Cc: mina86@mina86.com, akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rabin Vincent Subject: Re: [PATCH 2/2] ARM: dma-mapping: fix alloc/free for coherent + CMA + gfp=0 Message-ID: <20160219140600.GW19428@n2100.arm.linux.org.uk> References: <1455869524-13874-1-git-send-email-rabin.vincent@axis.com> <1455869524-13874-2-git-send-email-rabin.vincent@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455869524-13874-2-git-send-email-rabin.vincent@axis.com> 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 On Fri, Feb 19, 2016 at 09:12:04AM +0100, Rabin Vincent wrote: > Given a device which uses arm_coherent_dma_ops and on which > dev_get_cma_area(dev) returns non-NULL, the following usage of the DMA > API with gfp=0 results in a memory leak and memory corruption. > > p = dma_alloc_coherent(dev, sz, &dma, 0); > if (p) > dma_free_coherent(dev, sz, p, dma); > > The memory leak is because the alloc allocates using > __alloc_simple_buffer() but the free attempts > dma_release_from_contiguous(), which does not do free anything since the > page is not in the CMA area. I'd really like to see a better solution to this problem: over the course of the years, I've seen a number of patches that rearrange the test order at allocation time because of some problem or the other. What we need is a better way to ensure that we use the correct release functionality - having two independent set of tests where the order matters is really not very good. Maybe someone can put some thought into this... -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.