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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 A44CBC43219 for ; Sat, 4 May 2019 17:24:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A304205C9 for ; Sat, 4 May 2019 17:24:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="NrhwHrCg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727097AbfEDRYL (ORCPT ); Sat, 4 May 2019 13:24:11 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:45711 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726432AbfEDRYK (ORCPT ); Sat, 4 May 2019 13:24:10 -0400 Received: by mail-pf1-f195.google.com with SMTP id e24so4497635pfi.12; Sat, 04 May 2019 10:24:10 -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=0JVR+B0UU3TgsLiMAHGGrQRoriLTMKx5OUbcXksRlDc=; b=NrhwHrCg0m6lIyB40Emk1ksd8UDGBYE4QQkeWpHGEkFKzWtAB8HNQl/amDI2FVPdMX a3MBH2WXso6QDtLwZ8LInhkJyZbJdACglugp2WK1a1mGwrwNw5JeDQxlPcVoyt1ArHmj kgG05BnmgfEqJTunyjQNg3Asyg3hUW10b4wrdrZv34TPvjN4HXeBvjLfjtnX1Ahyowyi uxIGVDQajqOrz9Qnd7tZRLL/EOSwaSZrd9AB40rlpQjbZmLlwmv2tNgTg9wEjQ3ghF7j 25mHK4BEESYwMHNbw2Qwrz6p50D3Z+FsHW+pTpwZ9vD9Dpq/70cogv9fDI7o7hZQst+u 2jqg== 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=0JVR+B0UU3TgsLiMAHGGrQRoriLTMKx5OUbcXksRlDc=; b=o8npqdAh0OgnRqC6d45Y4ZzzdRY9HrGqvYByYd4sZX5MNz7UecoSyItFafLnpr22Vc kZQQxM34l6EZJd1OidYas+JteUzNSF/QVFxajsNk/xyGlG3O0ZvAhFA4o82I4UxXq0aN 8Ow0X0l2tG9VPDiPVLlq8b281G0vuTI9VlJl4F+vyWHvE7u5J/MVYKeBqAfhxSOZ0VJm jy813EG86xIMRTADARlnRuMiacKWVs6hMpQTX6AztOWr+Cby6OSJBtDTVR/ezWbfjG8J +UuVPCGsuA5ELx8/ZNdVeu0skT4QmophOwn9WmJt4gYULmHJIE/WuEJOAHo70/eiyIbW VASg== X-Gm-Message-State: APjAAAWMykSroUJkK8f4xWx263LWxDAxsW1upT2zUKnzbqbbNfSPdyYV v3QNnVZsvzn/TXkxrLsergg= X-Google-Smtp-Source: APXvYqzyt8fj+PtMYmfYVnfnoWHBpNYlydeIU8RPI/1Dvq2GoGrHyzbCh7vMR8XYPW3NDXgJ+ZCQ1g== X-Received: by 2002:a62:4690:: with SMTP id o16mr20782606pfi.166.1556990649903; Sat, 04 May 2019 10:24:09 -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 n9sm6965141pff.59.2019.05.04.10.24.07 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Sat, 04 May 2019 10:24:08 -0700 (PDT) Subject: Re: [PATCH] ipv4: Delete uncached routes upon unregistration of loopback device. To: Tetsuo Handa , "David S. Miller" Cc: David Ahern , Julian Anastasov , Cong Wang , syzbot , ddstreet@ieee.org, dvyukov@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, Linus Torvalds , Mahesh Bandewar References: <0000000000007d22100573d66078@google.com> <4684eef5-ea50-2965-86a0-492b8b1e4f52@I-love.SAKURA.ne.jp> <9d430543-33c3-0d9b-dc77-3a179a8e3919@I-love.SAKURA.ne.jp> <920ebaf1-ee87-0dbb-6805-660c1cbce3d0@I-love.SAKURA.ne.jp> <15b353e9-49a2-f08b-dc45-2e9bad3abfe2@i-love.sakura.ne.jp> <057735f0-4475-7a7b-815f-034b1095fa6c@gmail.com> <6e57bc11-1603-0898-dfd4-0f091901b422@i-love.sakura.ne.jp> <117fcc49-d389-c389-918f-86ccaef82e51@i-love.sakura.ne.jp> <70be7d61-a6fe-e703-978a-d17f544efb44@gmail.com> <40199494-8eb7-d861-2e3b-6e20fcebc0dc@i-love.sakura.ne.jp> <519ea12b-4c24-9e8e-c5eb-ca02c9c7d264@i-love.sakura.ne.jp> From: Eric Dumazet Message-ID: Date: Sat, 4 May 2019 13:24:07 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: 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 5/4/19 1:09 PM, Tetsuo Handa wrote: > On 2019/05/05 0:56, Eric Dumazet wrote:> >> Well, you have not fixed a bug, you simply made sure that whatever cpu is using the >> routes you forcibly deleted is going to crash the host very soon (use-after-frees have >> undefined behavior, but KASAN should crash most of the times) > > I confirmed that this patch survives "#syz test:" before submitting. > But you know that this patch is deleting the route entry too early. OK. > >> >> Please do not send patches like that with a huge CC list, keep networking patches >> to netdev mailing list. > > If netdev people started working on this "minutely crashing bug" earlier, > I would not have written a patch... So, just that you know, we are working on bug fixes, and this is best effort. It is not because _you_ want to fix a particular bug (out of hundreds) that we need to stop everything and work full time on a particular bug. And here the root cause of the problem is elsewhere. A dst is leaking somewhere, and prevents the netns dismantle. We had many dst leaks in the past, and they keep being added by new bugs. > >> >> Mahesh has an alternative patch, adding a fake device that can not be dismantled >> to make sure we fully intercept skbs sent through a dead route, instead of relying >> on loopback dropping them later at some point. > > So, the reason to temporarily move the refcount is to give enough period > so that the route entry is no longer used. But moving the refcount to a > loopback device in a namespace was wrong. Is this understanding correct? I believe you need spend more time on studying the networking code by yourself, add tracing if you believe this could be useful to you and others. > > Compared to moving the refcount to the loopback device in the init namespace, > the fake device can somehow drop the refcount moved via rt_flush_dev(), can't it? > The fake device wont ever disappear. > Anyway, I'll wait for Mahesh. >