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=-4.0 required=3.0 tests=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 E2C9BC43381 for ; Fri, 15 Mar 2019 22:43:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF1FE21872 for ; Fri, 15 Mar 2019 22:43:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727521AbfCOWn3 (ORCPT ); Fri, 15 Mar 2019 18:43:29 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:34612 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726953AbfCOWn3 (ORCPT ); Fri, 15 Mar 2019 18:43:29 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id E70C7140F4D21; Fri, 15 Mar 2019 15:43:28 -0700 (PDT) Date: Fri, 15 Mar 2019 15:43:28 -0700 (PDT) Message-Id: <20190315.154328.1054764537190173229.davem@davemloft.net> To: edumazet@google.com Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, syzkaller@googlegroups.com Subject: Re: [PATCH net] tun: properly test for IFF_UP From: David Miller In-Reply-To: <20190315031947.63245-1-edumazet@google.com> References: <20190315031947.63245-1-edumazet@google.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Fri, 15 Mar 2019 15:43:29 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Date: Thu, 14 Mar 2019 20:19:47 -0700 > Same reasons than the ones explained in commit 4179cb5a4c92 > ("vxlan: test dev->flags & IFF_UP before calling netif_rx()") > > netif_rx_ni() or napi_gro_frags() must be called under a strict contract. > > At device dismantle phase, core networking clears IFF_UP > and flush_all_backlogs() is called after rcu grace period > to make sure no incoming packet might be in a cpu backlog > and still referencing the device. > > A similar protocol is used for gro layer. > > Most drivers call netif_rx() from their interrupt handler, > and since the interrupts are disabled at device dismantle, > netif_rx() does not have to check dev->flags & IFF_UP > > Virtual drivers do not have this guarantee, and must > therefore make the check themselves. > > Fixes: 1bd4978a88ac ("tun: honor IFF_UP in tun_get_user()") > Signed-off-by: Eric Dumazet > Reported-by: syzbot Applied and queued up for -stable, thanks Eric.