Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752055Ab0FGFAF (ORCPT ); Mon, 7 Jun 2010 01:00:05 -0400 Received: from sh.osrg.net ([192.16.179.4]:36916 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751292Ab0FGFAD (ORCPT ); Mon, 7 Jun 2010 01:00:03 -0400 Date: Mon, 7 Jun 2010 13:59:48 +0900 To: mitov@issp.bas.bg Cc: fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org Subject: Re: [BUG][PATCH]dma-coherent.c: error path bug From: FUJITA Tomonori In-Reply-To: <201006070743.20226.mitov@issp.bas.bg> References: <201006070708.57453.mitov@issp.bas.bg> <20100607132631W.fujita.tomonori@lab.ntt.co.jp> <201006070743.20226.mitov@issp.bas.bg> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20100607135845B.fujita.tomonori@lab.ntt.co.jp> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (sh.osrg.net [192.16.179.4]); Mon, 07 Jun 2010 13:59:48 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2360 Lines: 53 On Mon, 7 Jun 2010 07:43:19 +0300 Marin Mitov wrote: > On Monday, June 07, 2010 07:27:49 am FUJITA Tomonori wrote: > > On Mon, 7 Jun 2010 07:08:56 +0300 > > Marin Mitov wrote: > > > > > On Monday, June 07, 2010 05:30:48 am FUJITA Tomonori wrote: > > > > On Sun, 6 Jun 2010 13:53:04 +0300 > > > > Marin Mitov wrote: > > > > > > > > > Hi all, > > > > > > > > > > The error path in dma_declare_coherent_memory() leaves > > > > > the pointer dev->dma_mem non completely initialized. > > > > > > > > > > If allocation of dev->dma_mem succeeds, > > > > > but allocation of dev->dma_mem->bitmap fails > > > > > dev->dma_mem is freed, but left non NULL > > > > > and non completely initialized. > > > > > > > > > > Either zero it after being freed (one liner patch), or assign to > > > > > dev->dma_mem only completely initialized structure (patch included). > > > > > > > > > > Comments welcome. > > > > > > > > > > Marin Mitov > > > > > > > > > > Signed-off-by: Marin Mitov > > > > > > > > Hmm, if dma_declare_coherent_memory() fails, the driver doesn't use > > > > dev->dma_mem. So even if dev->dma_mem points to a freed memory, I'm > > > > not sure that it causes a real problem. We could call this patch a > > > > cleanup though. > > > > > > > My understanding of dma_alloc_coherent() is that we first try to allocate from > > > per-device coherent memory and we do it using dma_alloc_from_coherent() > > > (in drivers/base/dma-coherent.c) if dev->dma_mem is not NULL (and we have > > > left it not NULL, here is the problem). If allocation of dev->dma_mem->bitmap > > > fails dev->dma_mem must be NULL. > > > > But are there any driver that can continue when dma_declare_coherent_memory() fails? > > > I do not know if such a real driver exists. >From a quick look, seems no. There is no fallback for such hardware, it's safe assumption, I guess. As I wrote, I don't think that the patch is rc material since seems that this doesn't cause a real problem. However, it looks fine for the next merge window. Thanks, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/