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=-9.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 4D338C07E9C for ; Wed, 7 Jul 2021 17:41:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3142861CC8 for ; Wed, 7 Jul 2021 17:41:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231158AbhGGRoa (ORCPT ); Wed, 7 Jul 2021 13:44:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230110AbhGGRo3 (ORCPT ); Wed, 7 Jul 2021 13:44:29 -0400 Received: from mail-wr1-x433.google.com (mail-wr1-x433.google.com [IPv6:2a00:1450:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E645C061574; Wed, 7 Jul 2021 10:41:48 -0700 (PDT) Received: by mail-wr1-x433.google.com with SMTP id a8so4017037wrp.5; Wed, 07 Jul 2021 10:41:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=lA3hDr792hgobfyrQMbraHH3m59ZWiVGpciRaq1+pUE=; b=vhIjqE2ALd4XXXh06sMcmJELw+L7AWFALPddHb12EhQNWJbZGClUcxJQ7fiPxegudN /OOZvxb78sHoZLxiSRg20Cmw5lInY60zs1HIUdYPzWnzNX97eHwB9DVadtWNTNXF313l +rNaOqMGGggXANoW8EPQKLeehcobgT4SRe+Wq6JNN69BxCTpFUGWrPFAFQPX1qyqbMoT 064ejKBH7k7lq4kDVpSi68JlnDkqKGt12KyliTICvFeeXFMNtsqyKTvccsYyYNb58+d4 mQr0PxIdbX2MvDeyxHQhTRvokOVwxHEKmUOxQNzhvcH2byuAn2fdQKfpzVCzN+8RFyRx NT3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=lA3hDr792hgobfyrQMbraHH3m59ZWiVGpciRaq1+pUE=; b=gPDmZd607Esb8NpaXAR2o2PdBeniezVqjYrznTpMQKbvSTU3a+UXjSoTZxZ2vdG8Q8 9TE7aVY3ByyT90oS4Ww1GN8Ivvg3njyt7KGwgjQk7oo5i/HeKdowjtqxtACmXKHKeIVj 9yy0On59G88NB58FdhbFRxOTdT3uizriRt9PEcaUyBnmqcq4gUhM3UM5j5v6TvrnYd1r fovubmWY3hu3YfQqyx06ek7Wf5yuw9uRhrf0hloTp9/OYNDwVIk5vDAvKNQyw459RpXh +yqjbrNyIaHbMDrapcRDCmIHRQaaQZbpCyvWdqyt/WtKBQijti3DzE/EY0hcvX9OjP58 lwVw== X-Gm-Message-State: AOAM533KV1RP+kZgS48aDCZxJDxsbYHRPxH9Po9/uqGjk6XJ5o9k+KXS QeFu+058W9HVjFzdMoKrSq8EHfPsdVA= X-Google-Smtp-Source: ABdhPJwbkbndjTycaWgmbiEB+6RtI4zIbh92o7Cw787TdRjf7dZaoUfxNq3A7M96i3Ct7Y1o08e70A== X-Received: by 2002:a05:6000:1361:: with SMTP id q1mr28751207wrz.179.1625679706809; Wed, 07 Jul 2021 10:41:46 -0700 (PDT) Received: from [192.168.98.98] (162.199.23.93.rev.sfr.net. [93.23.199.162]) by smtp.gmail.com with ESMTPSA id o11sm7671585wmc.2.2021.07.07.10.41.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Jul 2021 10:41:46 -0700 (PDT) Subject: Re: [PATCH IPV6 1/1] ipv6: allocate enough headroom in ip6_finish_output2() To: Jakub Kicinski , David Ahern Cc: Vasily Averin , "David S. Miller" , Hideaki YOSHIFUJI , David Ahern , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <3cb5a2e5-4e4c-728a-252d-4757b6c9612d@virtuozzo.com> <8996db63-5554-d3dc-cd36-94570ade6d18@gmail.com> <20210707094218.0e9b6ffc@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Eric Dumazet Message-ID: <1cbf3c7b-455e-f3a5-cc2c-c18ce8be4ce1@gmail.com> Date: Wed, 7 Jul 2021 19:41:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210707094218.0e9b6ffc@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/7/21 6:42 PM, Jakub Kicinski wrote: > On Wed, 7 Jul 2021 08:45:13 -0600 David Ahern wrote: >> On 7/7/21 8:04 AM, Vasily Averin wrote: >>> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c >>> index ff4f9eb..e5af740 100644 >>> --- a/net/ipv6/ip6_output.c >>> +++ b/net/ipv6/ip6_output.c >>> @@ -61,9 +61,24 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * >>> struct dst_entry *dst = skb_dst(skb); >>> struct net_device *dev = dst->dev; >>> const struct in6_addr *nexthop; >>> + unsigned int hh_len = LL_RESERVED_SPACE(dev); >>> struct neighbour *neigh; >>> int ret; >>> >>> + /* Be paranoid, rather than too clever. */ >>> + if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) { >>> + struct sk_buff *skb2; >>> + >>> + skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev)); >> >> why not use hh_len here? > > Is there a reason for the new skb? Why not pskb_expand_head()? pskb_expand_head() might crash, if skb is shared. We possibly can add a helper, factorizing all this, and eventually use pskb_expand_head() if safe.