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 6CDA0C433FE for ; Wed, 23 Nov 2022 16:09:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238815AbiKWQJr (ORCPT ); Wed, 23 Nov 2022 11:09:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238816AbiKWQJm (ORCPT ); Wed, 23 Nov 2022 11:09:42 -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 70936C4C0F for ; Wed, 23 Nov 2022 08:08:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669219720; 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=Mo9Cu02IrQqnqkR8eRuBSSZhf6FA5DQgEMy2KAnXWBA=; b=AV8Bonsu2txNrFl3MN9lTD5vCdQSr+ly5DFgikVl2AqewCh9F0zUTZu+jV23uupYwzvnwj szjWPyrU06UCDtSDQPWZy9UPLz5s8VYGsbNLzbREOdPXLPjZODiwYLarFopZNZIBQUtElm feXiJ9jxb6DdokLt911xhX2gtLr7g4M= Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-365-b-W3fVINMrurejh7MosUjg-1; Wed, 23 Nov 2022 11:08:39 -0500 X-MC-Unique: b-W3fVINMrurejh7MosUjg-1 Received: by mail-pf1-f199.google.com with SMTP id v16-20020a62a510000000b005745a58c197so1123591pfm.23 for ; Wed, 23 Nov 2022 08:08:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to:from :subject:cc:to:message-id:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=Mo9Cu02IrQqnqkR8eRuBSSZhf6FA5DQgEMy2KAnXWBA=; b=4AK4u7TXpvhP1S/0Q/huGcH+KDn3BW/wIW4pjcnm7o2areZqLXo8ri1Ia/Wp1pkbpb E963kfbkpslylAYfWSivfe7salqSP1kgqc1WVamQVo6XAxBOnmLJiZhEokNZlJOwBxvO UWuBO0+Z62tsEL+pRd8KAakbD4/E5sfpg+3Mqti7WJarB04H4jxCxW+3Jf0zltvSWken +qIsy8tqgRaPK2I4YzQOLLdyuk69QNTyUHEnW2ZjID4gjd2sxyzoskve3/JUyYKCbTih 10nK1OKoIstkf6Z0PnykdgGsfUMUOBiL48xcVTU/Q3B/ZtEa/P9wyg5qZjJ2WFfr48AQ jnxQ== X-Gm-Message-State: ANoB5pmAhaKSi5Mtfhvq5zATHFu/EQ1ubWhZ0Qsr+onNMxW4BvifBEZn VDUQbi+PKvBXv5adPbWNke8Fgmzdm143opBMPcRwF7Dzeei0mRUveHnPYeUzByUgG3DNtTYFf1r NRuGoTXcl4hNWGcsv X-Received: by 2002:a17:902:cf4b:b0:186:7a1d:b6ee with SMTP id e11-20020a170902cf4b00b001867a1db6eemr14339715plg.67.1669219716699; Wed, 23 Nov 2022 08:08:36 -0800 (PST) X-Google-Smtp-Source: AA0mqf6B1IjustAmXf1Mi4oCGfNiJDTbaeAzSvE594fNxzIXzV56SldvQdCxHnUGbv3jQagXoCnXtg== X-Received: by 2002:a17:902:cf4b:b0:186:7a1d:b6ee with SMTP id e11-20020a170902cf4b00b001867a1db6eemr14339673plg.67.1669219716324; Wed, 23 Nov 2022 08:08:36 -0800 (PST) Received: from localhost ([240d:1a:c0d:9f00:4f2f:926a:23dd:8588]) by smtp.gmail.com with ESMTPSA id n5-20020a170902e54500b001893e8ffa34sm2237343plf.97.2022.11.23.08.08.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Nov 2022 08:08:35 -0800 (PST) Date: Thu, 24 Nov 2022 01:08:31 +0900 (JST) Message-Id: <20221124.010831.156785940884442572.syoshida@redhat.com> To: jasowang@redhat.com Cc: edumazet@google.com, 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 Subject: Re: [PATCH v2] net: tun: Fix use-after-free in tun_detach() From: Shigeru Yoshida In-Reply-To: <88643033-45e1-3078-cb41-d7255ef874ad@redhat.com> References: <20221123.031005.476714651315933198.syoshida@redhat.com> <88643033-45e1-3078-cb41-d7255ef874ad@redhat.com> X-Mailer: Mew version 6.8 on Emacs 28.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Jason, On Wed, 23 Nov 2022 12:20:47 +0800, Jason Wang wrote: > > 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. Thank you so much for your comment. I'll prepare v3 patch to remove calling synchronize_rcu(). Thanks, Shigeru > 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 >>>>> >