Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60D7DC433EF for ; Mon, 3 Jan 2022 14:21:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233297AbiACOVo (ORCPT ); Mon, 3 Jan 2022 09:21:44 -0500 Received: from sin.source.kernel.org ([145.40.73.55]:45310 "EHLO sin.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233266AbiACOVm (ORCPT ); Mon, 3 Jan 2022 09:21:42 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 6A80DCE1107; Mon, 3 Jan 2022 14:21:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4884BC36AED; Mon, 3 Jan 2022 14:21:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641219695; bh=UScpXn/wm8MPz2o3vK9ue4lnQ9EvfPsRuqBaEo5WgYw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TBtkbLPvSGjqlU+VaYV806Rz6BMMNd0+EX0ytvXogTDsVT89fbSTUVg/GazuaPBVs C9s82SFmTN/YdtkbKx4cwthvrWT/kTOUE1YhKZV/AgMtPQ5AUTzNI3CmRdXy1tn0cA alspmctGNJca9RYQr6l7QCWrPsPpke32B4MaSpls= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Muchun Song , Cong Wang , Fam Zheng , Jakub Kicinski Subject: [PATCH 4.4 11/11] net: fix use-after-free in tw_timer_handler Date: Mon, 3 Jan 2022 15:21:22 +0100 Message-Id: <20220103142051.133867607@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220103142050.763904028@linuxfoundation.org> References: <20220103142050.763904028@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Muchun Song commit e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0 upstream. A real world panic issue was found as follow in Linux 5.4. BUG: unable to handle page fault for address: ffffde49a863de28 PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0 RIP: 0010:tw_timer_handler+0x20/0x40 Call Trace: call_timer_fn+0x2b/0x120 run_timer_softirq+0x1ef/0x450 __do_softirq+0x10d/0x2b8 irq_exit+0xc7/0xd0 smp_apic_timer_interrupt+0x68/0x120 apic_timer_interrupt+0xf/0x20 This issue was also reported since 2017 in the thread [1], unfortunately, the issue was still can be reproduced after fixing DCCP. The ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net namespace is destroyed since tcp_sk_ops is registered befrore ipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops in the list of pernet_list. There will be a use-after-free on net->mib.net_statistics in tw_timer_handler after ipv4_mib_exit_net if there are some inflight time-wait timers. This bug is not introduced by commit f2bf415cfed7 ("mib: add net to NET_ADD_STATS_BH") since the net_statistics is a global variable instead of dynamic allocation and freeing. Actually, commit 61a7e26028b9 ("mib: put net statistics on struct net") introduces the bug since it put net statistics on struct net and free it when net namespace is destroyed. Moving init_ipv4_mibs() to the front of tcp_init() to fix this bug and replace pr_crit() with panic() since continuing is meaningless when init_ipv4_mibs() fails. [1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1 Fixes: 61a7e26028b9 ("mib: put net statistics on struct net") Signed-off-by: Muchun Song Cc: Cong Wang Cc: Fam Zheng Cc: Link: https://lore.kernel.org/r/20211228104145.9426-1-songmuchun@bytedance.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv4/af_inet.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1770,6 +1770,10 @@ static int __init inet_init(void) tcp_v4_init(); + /* Initialise per-cpu ipv4 mibs */ + if (init_ipv4_mibs()) + panic("%s: Cannot init ipv4 mibs\n", __func__); + /* Setup TCP slab cache for open requests. */ tcp_init(); @@ -1798,12 +1802,6 @@ static int __init inet_init(void) if (init_inet_pernet_ops()) pr_crit("%s: Cannot init ipv4 inet pernet ops\n", __func__); - /* - * Initialise per-cpu ipv4 mibs - */ - - if (init_ipv4_mibs()) - pr_crit("%s: Cannot init ipv4 mibs\n", __func__); ipv4_proc_init();