From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753449AbcBWPYK (ORCPT ); Tue, 23 Feb 2016 10:24:10 -0500 Received: from mail-lf0-f48.google.com ([209.85.215.48]:32986 "EHLO mail-lf0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751544AbcBWPYI (ORCPT ); Tue, 23 Feb 2016 10:24:08 -0500 Date: Tue, 23 Feb 2016 16:23:53 +0100 From: Rabin Vincent To: Russell King - ARM Linux Cc: Rabin Vincent , 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: <20160223152353.GA22447@lnxrabinv.se.axis.com> References: <1455869524-13874-1-git-send-email-rabin.vincent@axis.com> <1455869524-13874-2-git-send-email-rabin.vincent@axis.com> <20160219140600.GW19428@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160219140600.GW19428@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 19, 2016 at 02:06:00PM +0000, Russell King - ARM Linux wrote: > 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. I've sent a v2 of this series which refactors the code so that we no longer have two independent sets of tests.