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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 4A6CCC2D0DB for ; Thu, 23 Jan 2020 10:44:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 276CC24125 for ; Thu, 23 Jan 2020 10:44:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726234AbgAWKoe (ORCPT ); Thu, 23 Jan 2020 05:44:34 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:56302 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726099AbgAWKoe (ORCPT ); Thu, 23 Jan 2020 05:44:34 -0500 Received: from localhost (unknown [185.13.106.231]) (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 6C8BF153DE704; Thu, 23 Jan 2020 02:44:30 -0800 (PST) Date: Thu, 23 Jan 2020 11:44:21 +0100 (CET) Message-Id: <20200123.114421.1414769180741959285.davem@davemloft.net> To: edumazet@google.com Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, syzkaller@googlegroups.com, ppenkov@google.com, willemb@google.com Subject: Re: [PATCH net] tun: add mutex_unlock() call and napi.skb clearing in tun_get_user() From: David Miller In-Reply-To: <20200122170735.4126-1-edumazet@google.com> References: <20200122170735.4126-1-edumazet@google.com> X-Mailer: Mew version 6.8 on Emacs 26.3 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]); Thu, 23 Jan 2020 02:44:33 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Date: Wed, 22 Jan 2020 09:07:35 -0800 > If both IFF_NAPI_FRAGS mode and XDP are enabled, and the XDP program > consumes the skb, we need to clear the napi.skb (or risk > a use-after-free) and release the mutex (or risk a deadlock) > > WARNING: lock held when returning to user space! > 5.5.0-rc6-syzkaller #0 Not tainted > ------------------------------------------------ > syz-executor.0/455 is leaving the kernel with locks still held! > 1 lock held by syz-executor.0/455: > #0: ffff888098f6e748 (&tfile->napi_mutex){+.+.}, at: tun_get_user+0x1604/0x3fc0 drivers/net/tun.c:1835 > > Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver") > Signed-off-by: Eric Dumazet > Reported-by: syzbot Applied and queued up for -stable, thanks Eric.