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=-15.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 5B2D5C433DB for ; Mon, 1 Feb 2021 14:11:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E15164DBD for ; Mon, 1 Feb 2021 14:11:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231796AbhBAOLk (ORCPT ); Mon, 1 Feb 2021 09:11:40 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:7522 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229500AbhBAOLi (ORCPT ); Mon, 1 Feb 2021 09:11:38 -0500 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 111E33rv088288; Mon, 1 Feb 2021 09:10:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=kFfdiVRSosOPGBsI44S5SiAq787FhllDr5Y5F5u5cYQ=; b=cs8rpuv8dySai1YarWb142wHJt556SoyMPcuFzcwp/hyMhhz9qnOko+MBSlIlr4LGGBx qdh79pg3YjpLZv3J76TZF/TOkFBKnJK+yUWPkJ5DsaiaL+aUwPTrHb38b4LPazQrKvwB GascykC2BjdBQuHzxWOfyV3o54rGpoEx3fXR7x6YV8XT/TZUQGmi7MU0yN0JsYWF66oJ U67TsnkaZV5ced82dUM2xDXPz30M/FnOi9iQuTuaBA2KZGCsKPbWbVCSq5N7ut2V7o3k sD4oKDZ5P/dNvk+vGhWRYQPj2USdEq6nqcNdHe+q6RlXUdfKToIUm6w74LlTLyEr3r6J NA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 36ejj0sjs3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 01 Feb 2021 09:10:53 -0500 Received: from m0098394.ppops.net (m0098394.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 111E39Iq088662; Mon, 1 Feb 2021 09:10:51 -0500 Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com with ESMTP id 36ejj0sjq1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 01 Feb 2021 09:10:51 -0500 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 111E4DIf021029; Mon, 1 Feb 2021 14:10:48 GMT Received: from b06avi18878370.portsmouth.uk.ibm.com (b06avi18878370.portsmouth.uk.ibm.com [9.149.26.194]) by ppma02fra.de.ibm.com with ESMTP id 36cy38904p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 01 Feb 2021 14:10:47 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 111EAbMX32440762 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 1 Feb 2021 14:10:37 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BB97011C052; Mon, 1 Feb 2021 14:10:45 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 73DBB11C04C; Mon, 1 Feb 2021 14:10:45 +0000 (GMT) Received: from [9.145.70.87] (unknown [9.145.70.87]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 1 Feb 2021 14:10:45 +0000 (GMT) Subject: Re: [PATCH net] net: lapb: Copy the skb before sending a packet To: Xie He , "David S. Miller" , Jakub Kicinski , linux-x25@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Martin Schiller References: <20210201055706.415842-1-xie.he.0141@gmail.com> From: Julian Wiedmann Message-ID: <4d1988d9-6439-ae37-697c-d2b970450498@linux.ibm.com> Date: Mon, 1 Feb 2021 15:10:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210201055706.415842-1-xie.he.0141@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.737 definitions=2021-02-01_05:2021-01-29,2021-02-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 bulkscore=0 suspectscore=0 adultscore=0 impostorscore=0 phishscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102010068 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01.02.21 06:57, Xie He wrote: > When sending a packet, we will prepend it with an LAPB header. > This modifies the shared parts of a cloned skb, so we should copy the > skb rather than just clone it, before we prepend the header. > > In "Documentation/networking/driver.rst" (the 2nd point), it states > that drivers shouldn't modify the shared parts of a cloned skb when > transmitting. > This sounds a bit like you want skb_cow_head() ... ? > The "dev_queue_xmit_nit" function in "net/core/dev.c", which is called > when an skb is being sent, clones the skb and sents the clone to > AF_PACKET sockets. Because the LAPB drivers first remove a 1-byte > pseudo-header before handing over the skb to us, if we don't copy the > skb before prepending the LAPB header, the first byte of the packets > received on AF_PACKET sockets can be corrupted. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: Martin Schiller > Signed-off-by: Xie He > --- > net/lapb/lapb_out.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/lapb/lapb_out.c b/net/lapb/lapb_out.c > index 7a4d0715d1c3..a966d29c772d 100644 > --- a/net/lapb/lapb_out.c > +++ b/net/lapb/lapb_out.c > @@ -82,7 +82,8 @@ void lapb_kick(struct lapb_cb *lapb) > skb = skb_dequeue(&lapb->write_queue); > > do { > - if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) { > + skbn = skb_copy(skb, GFP_ATOMIC); > + if (!skbn) { > skb_queue_head(&lapb->write_queue, skb); > break; > } >