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=-17.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 BDA13C4320A for ; Thu, 5 Aug 2021 12:55:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 981AB61152 for ; Thu, 5 Aug 2021 12:55:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241535AbhHEMzg (ORCPT ); Thu, 5 Aug 2021 08:55:36 -0400 Received: from relay.sw.ru ([185.231.240.75]:46324 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232615AbhHEMzf (ORCPT ); Thu, 5 Aug 2021 08:55:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=k7doBg0e3JXjBZq/zURAjt4EJ5ZAbtwrV59dNqCZYJA=; b=zEm0nOAsAaQ7PAk+4 10tK5qsVpCEZi2uwaq6GIjMXzj95niq3fpstkC6W5zCcwKpUQHuOt7Sh/uO/bFfIQlki36J6O4MLr a4E3SeGJLE2fMRFcupv2UoRVXWxG73CTf21LwyKzvN4RG6YxrYR4WTK08WbzJoSni0j5y0/AXgm+o =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mBcu4-006UwH-E1; Thu, 05 Aug 2021 15:55:16 +0300 Subject: Re: [PATCH NET v3 5/7] vrf: use skb_expand_head in vrf_finish_output To: Julian Wiedmann , "David S. Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , Eric Dumazet Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <15eba3b2-80e2-5547-8ad9-167d810ad7e3@virtuozzo.com> From: Vasily Averin Message-ID: <08c09fff-87f3-b29c-f681-88b031b0bb0d@virtuozzo.com> Date: Thu, 5 Aug 2021 15:55:15 +0300 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: 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 8/5/21 2:55 PM, Julian Wiedmann wrote: > On 02.08.21 11:52, Vasily Averin wrote: >> Unlike skb_realloc_headroom, new helper skb_expand_head >> does not allocate a new skb if possible. >> >> Signed-off-by: Vasily Averin >> --- >> drivers/net/vrf.c | 21 +++++++-------------- >> 1 file changed, 7 insertions(+), 14 deletions(-) >> > > [...] > >> /* 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)); >> - if (!skb2) { >> - ret = -ENOMEM; >> - goto err; >> + skb = skb_expand_head(skb, hh_len); >> + if (!skb) { >> + skb->dev->stats.tx_errors++; >> + return -ENOMEM; > > Hello Vasily, > > FYI, Coverity complains that we check skb != NULL here but then > still dereference skb->dev: > > > *** CID 1506214: Null pointer dereferences (FORWARD_NULL) > /drivers/net/vrf.c: 867 in vrf_finish_output() > 861 nf_reset_ct(skb); > 862 > 863 /* Be paranoid, rather than too clever. */ > 864 if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) { > 865 skb = skb_expand_head(skb, hh_len); > 866 if (!skb) { >>>> CID 1506214: Null pointer dereferences (FORWARD_NULL) >>>> Dereferencing null pointer "skb". > 867 skb->dev->stats.tx_errors++; > 868 return -ENOMEM; My fault, I missed it. Thank you, Vasily Averin