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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A5C90C433E1 for ; Fri, 31 Jul 2020 01:36:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86C842076B for ; Fri, 31 Jul 2020 01:36:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="L1u1vSnI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731057AbgGaBgh (ORCPT ); Thu, 30 Jul 2020 21:36:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728080AbgGaBgg (ORCPT ); Thu, 30 Jul 2020 21:36:36 -0400 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A8BBC061574; Thu, 30 Jul 2020 18:36:36 -0700 (PDT) Received: by mail-pl1-x644.google.com with SMTP id m16so15899740pls.5; Thu, 30 Jul 2020 18:36:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=unNkakX66uz1a8NwuDIWTVZkGEyN5ilSTI7FY3j0SNA=; b=L1u1vSnIvxCrTsbprGLnPNvMYpTghiUZV9ALHMPH/7GGcpcXgAkqsU/NHJ1vvMrck5 eAdHIPnKemAt37IRtdNBI6CN4RpCUiLxt/TRxso0w4MoHB4ojXMBdC1v1ebqYyKxe53y HNOHUXc9YjZffpb2dYNdlywhJg3y3CHsX2YmrGYzTsRazISvKoCWMMgBZOxL3QHcMeEL iFTKkkOpibBFDnNqOwZlPNPuoOzcXXZmvikjntTvHVA+ajhwh3wxmBWSy7Dnm9Fw/JNX Lde2+mZcbbo9Mg8FR0UVbg5G+sZdcITWW1fs1AlQOjQm4O4rBA1ZCn9Tf3PJhFxvWIty 7IDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=unNkakX66uz1a8NwuDIWTVZkGEyN5ilSTI7FY3j0SNA=; b=cwPNBjm302yaoWye58I2qxYn3tWv0qc/JDbF+8ZA++TWewrE3BuzKtDbIhtxTar+lT paIXt/HZy6A6wvvFGqwsqU8vOmo0YU5BRSNVDwqoryAd/0wvW5HHMvgR8rjc7OciHubd qBP8I3W7/GDnnPuRVPHm+Pxwky/WMmipJT9TOxLESuH978/SC8oNpHs+Wvqte3cWa4k8 w1LcXyMxenoqhBdihMqBDbOm26aqhVNBUs8amyP28oT2o1d6WuroLrSMIqCf8d0MPMzv MFnAP83p/v331CiLxOQ+rcoNgwvZd/37ZLgwhDhezpdbFznVJDWuPJYNvUAaXIfsOpZM +lhg== X-Gm-Message-State: AOAM5331PyA0xL/YwOJQ0KxDV7h7qaJkEu1c9HanCYnbNHjaosTaWmkn QHie1VHnICfLkwZbpokW5C6HHtw/xgWOcUDmGGYsZskY X-Google-Smtp-Source: ABdhPJzVA+O/8B02DuuSBuOGAZP7Ze1ToCSzfGnOyyBIPv80gzyS07s2MKeTbAYxBcysu6qbfmsN3xD6FR+kU5LkJ3I= X-Received: by 2002:a63:e057:: with SMTP id n23mr1471867pgj.368.1596159395958; Thu, 30 Jul 2020 18:36:35 -0700 (PDT) MIME-Version: 1.0 References: <20200730073702.16887-1-xie.he.0141@gmail.com> In-Reply-To: <20200730073702.16887-1-xie.he.0141@gmail.com> From: Xie He Date: Thu, 30 Jul 2020 18:36:25 -0700 Message-ID: Subject: Re: [PATCH v2] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len To: Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Linux Kernel Network Developers , LKML , Linux X25 Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org I'm really sorry to have re-sent the patch when the patch is still in review. I don't intend to be disrespectful to anyone. And I apologize for any disrespectfulness this might appear. Sorry. I'm also sorry for not having sent the patch with the proper subject prefixed with "net" or "net-next". If anyone requests I can re-send this patch with the proper subject "PATCH net". This patch actually fixes a kernel panic when this driver is used with a AF_PACKET/RAW socket. This driver runs on top of Ethernet interfaces. So I created a pair of virtual Ethernet (veth) interfaces, loaded this driver to create a pair of X.25 interfaces on top of them, and wrote C programs to use AF_PACKET sockets to send/receive data through them. At first I used AF_PACKET/DGRAM sockets. I prepared packet data according to the requirements of X.25 drivers. I first sent an one-byte packet ("\x01") to instruct the driver to connect, then I sent data prefixed with an one-byte pseudo header ("\x00") to instruct the driver to send the data, and then I sent another one-byte packet ("\x02") to instruct the driver to disconnect. This works fine with AF_PACKET/DGRAM sockets. However, when I change it to AF_PACKET/RAW sockets, kernel panic occurs. The stack trace is as follows. We can see the kernel panicked because of insufficient header space when pushing the Ethernet header. [ 168.399197] skbuff: skb_under_panic: text:ffffffff819d95fb len:20 put:14 head:ffff8882704c0a00 data:ffff8882704c09fd tail:0x11 end:0xc0 dev:veth0 ... [ 168.399255] Call Trace: [ 168.399259] skb_push.cold+0x14/0x24 [ 168.399262] eth_header+0x2b/0xc0 [ 168.399267] lapbeth_data_transmit+0x9a/0xb0 [lapbether] [ 168.399275] lapb_data_transmit+0x22/0x2c [lapb] [ 168.399277] lapb_transmit_buffer+0x71/0xb0 [lapb] [ 168.399279] lapb_kick+0xe3/0x1c0 [lapb] [ 168.399281] lapb_data_request+0x76/0xc0 [lapb] [ 168.399283] lapbeth_xmit+0x56/0x90 [lapbether] [ 168.399286] dev_hard_start_xmit+0x91/0x1f0 [ 168.399289] ? irq_init_percpu_irqstack+0xc0/0x100 [ 168.399291] __dev_queue_xmit+0x721/0x8e0 [ 168.399295] ? packet_parse_headers.isra.0+0xd2/0x110 [ 168.399297] dev_queue_xmit+0x10/0x20 [ 168.399298] packet_sendmsg+0xbf0/0x19b0 ...... After applying this patch, the kernel panic no longer appears, and AF_PACKET/RAW sockets would then behave the same as AF_PACKET/DGRAM sockets.