From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71972C6778F for ; Wed, 25 Jul 2018 07:13:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0604620844 for ; Wed, 25 Jul 2018 07:13:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0604620844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728693AbeGYIYG (ORCPT ); Wed, 25 Jul 2018 04:24:06 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:10120 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728658AbeGYIYG (ORCPT ); Wed, 25 Jul 2018 04:24:06 -0400 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id D38A383753B3E; Wed, 25 Jul 2018 15:13:42 +0800 (CST) Received: from [127.0.0.1] (10.177.31.96) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.382.0; Wed, 25 Jul 2018 15:13:36 +0800 Subject: Re: [PATCH v2] ARM: dma-mapping: always clear allocated buffers To: , , References: <20180725070706.19576-1-yuehaibing@huawei.com> CC: , , , , , , , , , Christoph Hellwig From: YueHaibing Message-ID: Date: Wed, 25 Jul 2018 15:13:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20180725070706.19576-1-yuehaibing@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.31.96] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +CC Christoph Hellwig On 2018/7/25 15:07, YueHaibing wrote: > Sean Wang reported dma_zalloc_coherent doesn't work as expect on his > armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool > doesn't honor __GFP_ZERO. > > As commit 6829e274a623 ("arm64: dma-mapping: always clear allocated buffers") > has pointed out,buffers allocated by dma_alloc_coherent() are always zeroed > on most architectures. some drivers rely on this 'feature'. Allocated buffer > might be also exposed to userspace with dma_mmap() call,so clearing it is > desired from security point of view to avoid exposing random memory to userspace. > > This patch unifies dma_alloc_coherent() behavior on ARM architecture with other > implementations by unconditionally zeroing allocated buffer.Also to fix > dma_zalloc_coherent behavior. > > Reported-by: Sean Wang > Signed-off-by: YueHaibing > Reviewed-by: zhong jiang > --- > v2: reference more argument from arm64 commit as Christoph suggested > --- > arch/arm/mm/dma-mapping.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 6656647..cf5882f 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -564,6 +564,7 @@ static void *__alloc_from_pool(size_t size, struct page **ret_page) > > *ret_page = phys_to_page(phys); > ptr = (void *)val; > + memset(ptr, 0, size); > } > > return ptr; >