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=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 D92A1C43381 for ; Thu, 14 Mar 2019 12:58:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA3F820854 for ; Thu, 14 Mar 2019 12:58:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WAW2N4oN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727413AbfCNM6H (ORCPT ); Thu, 14 Mar 2019 08:58:07 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:37271 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727057AbfCNM6H (ORCPT ); Thu, 14 Mar 2019 08:58:07 -0400 Received: by mail-pg1-f194.google.com with SMTP id q206so3930497pgq.4 for ; Thu, 14 Mar 2019 05:58:06 -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=pHU7ws753BbC5/aMiT0hQiqohifagVWVSLy+Wfsf+o8=; b=WAW2N4oN3yM+Jrsi6EMs1RikvBaicXcagERdbH+pPz8ZS2geh8k2sR1vW6wZgcgj1o me2iema/tMlAV3oLRLKWTdGwW6E54R/8lWnAWuXm7SXUcYMkpTMzvA8wCW3RtxkZ6NIc vjkXEX2MiY+bp1DOKdIhsBttju9SA5eEUVMbq7R/vTw9p2029sSqYmvprGH83xf7/NFa kUm03qn6xhaN/xvg7DUvSC0M2woQzYS/Fc+HRP7nhu5BR9A3MQuTL0cfgazXbV0cKKuT B0S2qcFVezLqxYVF86dW6h9vmqUVPDzVd8HNBFUax/cGF/MT68izw5My+rioVfkQHebR VkMw== 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=pHU7ws753BbC5/aMiT0hQiqohifagVWVSLy+Wfsf+o8=; b=kRQHC8ah/rNKnXPPN10osYuZJ9QMlq87sho22c2NrFb8bZRQ3h25agJcqEnnv0b4r2 3aruMwGMUtV8zVNLkfSbsssegjHEzVJV8qcWXvBW3REfyclmnttOrVbmXKKH/rL/bje/ Gguh1t1hgP/WPKLN5q/voyAJ/d1zQz/3KnzRzQCi4hzjknknyKdCjNIUpXZ6S0DeJMzw DG1YGY7h4uqWWQ/8/rXKSpeeT2/BGUTTIP10ISTf6l0MAYCzmvvDIQ++ZluO1aoKZuTr LaAiJX2awsAz9gVHt2Uq2IkWht9r9yHcuIFvXutnd4rc8huYcED2U4pmygLtbMWkvIF1 O29A== X-Gm-Message-State: APjAAAUuS9OmQEeHOjmn2LINEvNB1kXbCM0PwovJBkEDHkychq4vXZV5 G3JrHIJDGrPTmn7QM454RkA= X-Google-Smtp-Source: APXvYqwD/uCM/EAzr5MHVkBwx6hF2jW4gJcNQDlxCSEetmvxZq2rmCGfPOuPIlyUEmG/6XakNFMu4A== X-Received: by 2002:a65:4844:: with SMTP id i4mr43677230pgs.347.1552568286149; Thu, 14 Mar 2019 05:58:06 -0700 (PDT) Received: from [192.168.86.235] (c-73-241-150-70.hsd1.ca.comcast.net. [73.241.150.70]) by smtp.gmail.com with ESMTPSA id z6sm1471723pgp.8.2019.03.14.05.58.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Mar 2019 05:58:05 -0700 (PDT) Subject: Re: [PATCH net] net: enforce xmit_recursion for devices with a queue To: Sabrina Dubroca , netdev@vger.kernel.org Cc: Eric Dumazet , Jianlin Shi , Stefano Brivio References: <6d9ed6c448a5c855e05abf19c205f33a66b6ff40.1552557395.git.sd@queasysnail.net> From: Eric Dumazet Message-ID: Date: Thu, 14 Mar 2019 05:58:03 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <6d9ed6c448a5c855e05abf19c205f33a66b6ff40.1552557395.git.sd@queasysnail.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 03/14/2019 03:15 AM, Sabrina Dubroca wrote: > Commit 745e20f1b626 ("net: add a recursion limit in xmit path") > introduced a recursion limit, but it only applies to devices without a > queue. Virtual devices with a queue (either because they don't have > the IFF_NO_QUEUE flag, or because the administrator added one) can > still cause an unbounded recursion, via __dev_queue_xmit -> > __dev_xmit_skb -> qdisc_run -> __qdisc_run -> qdisc_restart -> > sch_direct_xmit -> dev_hard_start_xmit . Jianlin reported this in a > setup with 16 gretap devices stacked on top of one another. > > This patch prevents the stack overflow by incrementing xmit_recursion in > code paths that can call dev_hard_start_xmit() (like commit 745e20f1b626 > did). If the recursion limit is exceeded, the packet is enqueued and the > qdisc is scheduled. > > Reported-by: Jianlin Shi > Signed-off-by: Sabrina Dubroca > Reviewed-by: Stefano Brivio Hi Sabrina, thanks for the patch. Can't we detect this in the control path instead ? Surely this makes no sense in real world to stack 16 devices like that.