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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_SANE_1 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 D30A9C433E0 for ; Sat, 27 Jun 2020 13:09:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ADD0621548 for ; Sat, 27 Jun 2020 13:09:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Ql8e9lUt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726645AbgF0NJs (ORCPT ); Sat, 27 Jun 2020 09:09:48 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:37336 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726439AbgF0NJs (ORCPT ); Sat, 27 Jun 2020 09:09:48 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05RCwW3Q157642; Sat, 27 Jun 2020 13:09:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2020-01-29; bh=y6Z3ndKwcdvb/o527oos0Vmmml29kOeFL0WHa87IivU=; b=Ql8e9lUtJMlfraXeMxmr7CbqCK9xuMbtf7EWIRx61zzfGC2opBP3kGLATC2sx1f0RDA2 d0Lvy+oGkcU29Lff/OVWhty22/vB9iokcaJ6FClpQ297FuDtl5L2ayJQDzxF7ZNUJmmv E0efY9Sop8sMj7xOUd25EAaXgcWhXaz9lpxi4auYpPgM6aHGFBgG/WaPE1HNt+Bf+UoY 5LFHxswr0Nv7qmXarlD7O7Bocr93+xlVe3um0N5oefhuS5x2pIEkyzqdCUFhcMDumXn1 hrpafsd3CKEf2aQ9rCHTQgUpIIQRcKEDTyGq285awLJVP5wytvkyghJUfa8F/Boo0Oup Ow== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2120.oracle.com with ESMTP id 31wxrmru6e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Sat, 27 Jun 2020 13:09:25 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05RCvZxY049144; Sat, 27 Jun 2020 13:09:25 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 31wu7s3k7j-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 27 Jun 2020 13:09:25 +0000 Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 05RD9Mij009209; Sat, 27 Jun 2020 13:09:22 GMT Received: from kadam (/41.57.98.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sat, 27 Jun 2020 13:09:21 +0000 Date: Sat, 27 Jun 2020 16:09:15 +0300 From: Dan Carpenter To: Richard Weinberger Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, sumit.semwal@linaro.org, robin.murphy@arm.com, m.szyprowski@samsung.com, hch@lst.de Subject: Re: Passing NULL dev to dma_alloc_coherent() allowed or not? Message-ID: <20200627130915.GF2571@kadam> References: <1669515915.65540.1593258316061.JavaMail.zimbra@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1669515915.65540.1593258316061.JavaMail.zimbra@nod.at> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9664 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 bulkscore=0 spamscore=0 malwarescore=0 adultscore=0 mlxscore=0 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006270095 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9664 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 mlxlogscore=999 priorityscore=1501 impostorscore=0 bulkscore=0 clxscore=1011 malwarescore=0 phishscore=0 adultscore=0 cotscore=-2147483648 lowpriorityscore=0 suspectscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006270095 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 27, 2020 at 01:45:16PM +0200, Richard Weinberger wrote: > Hi! > > While porting on an old out-of-tree driver I noticed that dma_alloc_coherent() > was used with dev being NULL. > > commit 148a97d5a02a62f81b5d6176f871c94a65e1f3af > Author: Dan Carpenter > Date: Wed Apr 24 17:24:37 2019 +0300 > > dma-mapping: remove an unnecessary NULL check > > We already dereferenced "dev" when we called get_dma_ops() so this NULL > check is too late. We're not supposed to pass NULL "dev" pointers to > dma_alloc_attrs(). > > Signed-off-by: Dan Carpenter > Signed-off-by: Christoph Hellwig > > says that dma_alloc_attrs() with dev being NULL is not allowed, but in > include/linux/dma-mapping.h we have: > > static inline void *dma_alloc_coherent(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp) > { > > return dma_alloc_attrs(dev, size, dma_handle, gfp, > (gfp & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0); > } > > In Linus' tree I see at least three callers of dma_alloc_coherent() with a NULL device. > drivers/staging/emxx_udc/emxx_udc.c:2596: ep->virt_buf = dma_alloc_coherent(NULL, PAGE_SIZE, > drivers/tty/synclink.c:3667: info->buffer_list = dma_alloc_coherent(NULL, BUFFERLISTSIZE, &info->buffer_list_dma_addr, GFP_KERNEL); > drivers/tty/synclink.c:3777: BufferList[i].virt_addr = dma_alloc_coherent(NULL, DMABUFFERSIZE, &BufferList[i].dma_addr, GFP_KERNEL); > > I think these callers are wrong. > Can you please clarify? The are wrong. It was slightly worse when I originally sent the patch but we fixed comedi. https://lkml.org/lkml/2019/4/24/668 regards, dan carpenter