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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33BBCC4332F for ; Wed, 23 Nov 2022 04:26:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235756AbiKWE0H (ORCPT ); Tue, 22 Nov 2022 23:26:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235875AbiKWEZk (ORCPT ); Tue, 22 Nov 2022 23:25:40 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EE2CE9165 for ; Tue, 22 Nov 2022 20:20:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669177258; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WIloXbDe6Xf5V7hRDZwNW8sxVxxV79aT2COzbooV/8o=; b=OqWgyb8R3fgVxtSZ0xkTSLDHmwy7iguirE/x0bp6QazIZQjgZfdnf6wefchq0jD0hYLoer jKEI/8X17ST/IlyMur8OiJ4N1b8V7Q81W6aIDZ+RlPCI6E+X1ccALn5n0LVKkP0Q0LxtVB li6rq52BRenQMj7L4UYjlUe1RBZSUkc= Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-41-V4G4sybDPZa2Dda1FX-A8Q-1; Tue, 22 Nov 2022 23:20:56 -0500 X-MC-Unique: V4G4sybDPZa2Dda1FX-A8Q-1 Received: by mail-pj1-f72.google.com with SMTP id my9-20020a17090b4c8900b002130d29fd7cso509085pjb.7 for ; Tue, 22 Nov 2022 20:20:56 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=WIloXbDe6Xf5V7hRDZwNW8sxVxxV79aT2COzbooV/8o=; b=zFFWPGEZst82sXpMEI5VRbWdlUjfTU6MVl6btB6w1NsImxxNgkjzc5S9TCcNHL168B sLntRSQ8ZTdCkObCEmiRzGDzA4cPWHdABr3b6VhhikJzsZ7crBaaht2WJOEAVXQUCftr SI6zzlT/zOsrZjKOxHUa89lD8K7Hs6TaYywzoopM/Ukriyf6FK9sHb8sxHVZFjQQV2WZ uqXxt1tcOEWXKqFhVa1+d3VBRkSRCJV2L2sB5iJ3JydwAO3KwhtvILx3b3O+VOwviTAN N74Tn/QQp1SAv7quhOg0/MIoVPzMNcB4nOPJnBOvR9OhZvOK2x5aPs/Q1bzgbqVwwzkk KDBA== X-Gm-Message-State: ANoB5plH5CenOnmvGpz3mNf08m3h/VtWhM1tSdsKUBcrcCNgYI5MZ2Ot EF2m0KoMB9Xn/cWw7WkCNb5iXsYMRpwGglaeKH2eIlQpbvXIzIgZQcY7XaL1bqr3KHeRAhwvUW7 YmAf3i7CQDbOQiK0PQUYa61Nt X-Received: by 2002:a17:90a:4b4d:b0:218:b2da:1091 with SMTP id o13-20020a17090a4b4d00b00218b2da1091mr13456792pjl.154.1669177255642; Tue, 22 Nov 2022 20:20:55 -0800 (PST) X-Google-Smtp-Source: AA0mqf7wOf2Zw6T2jczoJNsiubvwnOuZb/A3PpE3Jw9LSXqJcak1g13OXdGfx5velA/NGlNiwWppmQ== X-Received: by 2002:a17:90a:4b4d:b0:218:b2da:1091 with SMTP id o13-20020a17090a4b4d00b00218b2da1091mr13456777pjl.154.1669177255314; Tue, 22 Nov 2022 20:20:55 -0800 (PST) Received: from [10.72.12.114] ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id h3-20020a170902b94300b00183c6784704sm5516850pls.291.2022.11.22.20.20.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Nov 2022 20:20:54 -0800 (PST) Message-ID: <88643033-45e1-3078-cb41-d7255ef874ad@redhat.com> Date: Wed, 23 Nov 2022 12:20:47 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH v2] net: tun: Fix use-after-free in tun_detach() Content-Language: en-US To: Eric Dumazet , Shigeru Yoshida Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+106f9b687cd64ee70cd1@syzkaller.appspotmail.com References: <20221120090213.922567-1-syoshida@redhat.com> <20221123.031005.476714651315933198.syoshida@redhat.com> From: Jason Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/11/23 02:47, Eric Dumazet 写道: > On Tue, Nov 22, 2022 at 10:10 AM Shigeru Yoshida wrote: >> Hi Eric, >> >> On Mon, 21 Nov 2022 08:47:17 -0800, Eric Dumazet wrote: >>> On Sun, Nov 20, 2022 at 1:02 AM Shigeru Yoshida wrote: >>>> syzbot reported use-after-free in tun_detach() [1]. This causes call >>>> trace like below: >>>> >>>> ================================================================== >>>> BUG: KASAN: use-after-free in notifier_call_chain+0x1ee/0x200 kernel/notifier.c:75 >>>> Read of size 8 at addr ffff88807324e2a8 by task syz-executor.0/3673 >>>> >>>> CPU: 0 PID: 3673 Comm: syz-executor.0 Not tainted 6.1.0-rc5-syzkaller-00044-gcc675d22e422 #0 >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 >>>> Call Trace: >>>> >>>> __dump_stack lib/dump_stack.c:88 [inline] >>>> dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 >>>> print_address_description mm/kasan/report.c:284 [inline] >>>> print_report+0x15e/0x461 mm/kasan/report.c:395 >>>> kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 >>>> notifier_call_chain+0x1ee/0x200 kernel/notifier.c:75 >>>> call_netdevice_notifiers_info+0x86/0x130 net/core/dev.c:1942 >>>> call_netdevice_notifiers_extack net/core/dev.c:1983 [inline] >>>> call_netdevice_notifiers net/core/dev.c:1997 [inline] >>>> netdev_wait_allrefs_any net/core/dev.c:10237 [inline] >>>> netdev_run_todo+0xbc6/0x1100 net/core/dev.c:10351 >>>> tun_detach drivers/net/tun.c:704 [inline] >>>> tun_chr_close+0xe4/0x190 drivers/net/tun.c:3467 >>>> __fput+0x27c/0xa90 fs/file_table.c:320 >>>> task_work_run+0x16f/0x270 kernel/task_work.c:179 >>>> exit_task_work include/linux/task_work.h:38 [inline] >>>> do_exit+0xb3d/0x2a30 kernel/exit.c:820 >>>> do_group_exit+0xd4/0x2a0 kernel/exit.c:950 >>>> get_signal+0x21b1/0x2440 kernel/signal.c:2858 >>>> arch_do_signal_or_restart+0x86/0x2300 arch/x86/kernel/signal.c:869 >>>> exit_to_user_mode_loop kernel/entry/common.c:168 [inline] >>>> exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 >>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] >>>> syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 >>>> do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 >>>> entry_SYSCALL_64_after_hwframe+0x63/0xcd >>>> >>>> The cause of the issue is that sock_put() from __tun_detach() drops >>>> last reference count for struct net, and then notifier_call_chain() >>>> from netdev_state_change() accesses that struct net. >>>> >>>> This patch fixes the issue by calling sock_put() from tun_detach() >>>> after all necessary accesses for the struct net has done. >>>> >>>> Fixes: 83c1f36f9880 ("tun: send netlink notification when the device is modified") >>>> Reported-by: syzbot+106f9b687cd64ee70cd1@syzkaller.appspotmail.com >>>> Link: https://syzkaller.appspot.com/bug?id=96eb7f1ce75ef933697f24eeab928c4a716edefe [1] >>>> Signed-off-by: Shigeru Yoshida >>>> --- >>>> v2: >>>> - Include symbolic stack trace >>>> - Add Fixes and Reported-by tags >>>> v1: https://lore.kernel.org/all/20221119075615.723290-1-syoshida@redhat.com/ >>>> --- >>>> drivers/net/tun.c | 6 +++++- >>>> 1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >>>> index 7a3ab3427369..ce9fcf4c8ef4 100644 >>>> --- a/drivers/net/tun.c >>>> +++ b/drivers/net/tun.c >>>> @@ -686,7 +686,6 @@ static void __tun_detach(struct tun_file *tfile, bool clean) >>>> if (tun) >>>> xdp_rxq_info_unreg(&tfile->xdp_rxq); >>>> ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); >>>> - sock_put(&tfile->sk); >>>> } >>>> } >>>> >>>> @@ -702,6 +701,11 @@ static void tun_detach(struct tun_file *tfile, bool clean) >>>> if (dev) >>>> netdev_state_change(dev); >>>> rtnl_unlock(); >>>> + >>>> + if (clean) { >>> Would you mind explaining (a comment would be nice) why this barrier is needed ? >> I thought that tfile is accessed with rcu_lock(), so I put >> synchronize_rcu() here. Please let me know if I misunderstand the >> concept of rcu (I'm losing my confidence...). >> > Addin Jason for comments. > > If an RCU grace period was needed before commit 83c1f36f9880 ("tun: > send netlink notification when the device is modified"), > would we need another patch ? I think we don't need another synchronization here. __tun_detach() has already done the necessary synchronization when it tries to modify tun->tfiles array and tfile->tun. Thanks > > Also sock_flag(sk, SOCK_RCU_FREE) would probably be better than adding > a synchronize_rcu() (if again a grace period is needed) > > > >> Thanks, >> Shigeru >> >>> Thanks. >>> >>>> + synchronize_rcu(); >>>> + sock_put(&tfile->sk); >>>> + } >>>> } >>>> >>>> static void tun_detach_all(struct net_device *dev) >>>> -- >>>> 2.38.1 >>>>