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=-3.6 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 4A76CC433E7 for ; Mon, 12 Oct 2020 22:26:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2E0C2078E for ; Mon, 12 Oct 2020 22:26:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vDAPCXD9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388809AbgJLW0y (ORCPT ); Mon, 12 Oct 2020 18:26:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388361AbgJLW0x (ORCPT ); Mon, 12 Oct 2020 18:26:53 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7585C0613D0 for ; Mon, 12 Oct 2020 15:26:53 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id l8so19349063ioh.11 for ; Mon, 12 Oct 2020 15:26:53 -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 :cc; bh=qFMTJJaoHl8g9jrSjPdss0thVlNcust6I6ikRgUYGS0=; b=vDAPCXD9CkuYa7Al2J4n04fyyzxIb8ivcwcVb0cXDrHr4YKc7oQT8bUKEtdQZYSwQm ld/eQYwFdbEzargl0QX3UkBKU7/hM27f2+WXW2wMMvAIhyLlVXqJZWW2Sl0aiPQRfrwQ vGUegqa+SRfo6ex2fDP6aoPfejgJyr2TX2h4TY+QQJx0q0Ku/YDUwrFukBghCWDpmS3r 2ZYdtHVHHFpepAIDME9+/T6U6qep4Bh5DWykWh4GGed6CQhNxV1R156DCkF9v2qZ9vL4 ZRuVXXo6IugNMxh7ndKrRX4gnHxYcDWPfKJidmEjrnIfl+o6IXhjX8eJ3rwonYedaCpB wr2w== 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:cc; bh=qFMTJJaoHl8g9jrSjPdss0thVlNcust6I6ikRgUYGS0=; b=KXbemTEHMM2cp6MZasfzewkLS13IXjr9eegTTAAXPEbs1Fy0duqBo3vDVwQB/VjtIf TQ5f15HXP0LFe6zO0DAnRbQrwYBYFGXZeN4JE4k1HJmZgbycvl1w4Ycy9wBgYqCSiQ1F Bmr2rfvDzUSRTlIX30fRcG7VPKjEI9yytBUiwpWn27VaufUQL+uF+YjM3B+hXcEpYnQ1 sVpGEq6jYcW/cv6fiiialZzQSW0gdza4/uKIQr+kbs0V5serQjS+ybzZHZZuMIweE+WO pcBPTqE8bdtEb2tgc7Ma35QEwzIv4QpVPXKlx5IccJG+hMznxvm3dE08I1yYVxSohfcp 3Q6A== X-Gm-Message-State: AOAM532lGCMybIEi/f1xbHwOu2Tc/tfJi/u2zFfORN+PSeIUl12hSzUm QQTqJlxm72xbbdhnsTVArMEtNMa4m8BSwk5ae5M= X-Google-Smtp-Source: ABdhPJxorbE5yy307fqNf+emS19zT9LeDHjTXzQrLW9URHUC4LUwsI3luV5c5Zyh0YAeBnVcbqUlt7K16MTrPn/2MXA= X-Received: by 2002:a02:94cd:: with SMTP id x71mr20269630jah.124.1602541613122; Mon, 12 Oct 2020 15:26:53 -0700 (PDT) MIME-Version: 1.0 References: <20201011191129.991-1-xiyou.wangcong@gmail.com> In-Reply-To: From: Cong Wang Date: Mon, 12 Oct 2020 15:26:41 -0700 Message-ID: Subject: Re: [Patch net v2] ip_gre: set dev->hard_header_len and dev->needed_headroom properly To: Xie He Cc: Linux Kernel Network Developers , syzbot , William Tu , Willem de Bruijn Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Oct 11, 2020 at 3:46 PM Xie He wrote: > > On Sun, Oct 11, 2020 at 12:11 PM Cong Wang wrote: > > > > @@ -626,8 +626,7 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb, > > > > if (dev->header_ops) { > > /* Need space for new headers */ > > - if (skb_cow_head(skb, dev->needed_headroom - > > - (tunnel->hlen + sizeof(struct iphdr)))) > > + if (skb_cow_head(skb, dev->hard_header_len)) > > goto free_skb; > > > > tnl_params = (const struct iphdr *)skb->data; > > As I understand, the skb_cow functions are for ensuring enough header > space before skb->data. (Right?) However, at this stage our skb->data > is already at the outer IP header, I think we don't need to request > additional header space before the outer IP header. Good point, I thought skb_headroom() == dev->hard_header_len, but skb->data already points to the tunnel header like you said, so we should pass 0 to skb_cow_head() here. Thanks.