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 17902C4332F for ; Tue, 22 Nov 2022 18:11:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232889AbiKVSLW (ORCPT ); Tue, 22 Nov 2022 13:11:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234463AbiKVSLO (ORCPT ); Tue, 22 Nov 2022 13:11:14 -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 DA30C7ECB0 for ; Tue, 22 Nov 2022 10:10:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669140613; 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=QoqA4TTHtwV1fAtIvj47WssSLUg61SUyeuraqKf8Rhg=; b=bZEMTG42zPVPXS98Jj2mRygcKwsievpoiS1gYR0XYio9NK2KouEAjXElXsomWi2c1OiDpb k8zId2pdQ5g/wDOPOsnzfqUIxF5iEUJ5FV5dZibkEBbRUdffRDCrsmFAL6FP/A4nwBxE4r C6sUZHA+nsgFi2cACMt0B22bJ1PeyVw= Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-343-6zpdR9fjNCSr8zXRsfKb4w-1; Tue, 22 Nov 2022 13:10:11 -0500 X-MC-Unique: 6zpdR9fjNCSr8zXRsfKb4w-1 Received: by mail-pg1-f198.google.com with SMTP id a33-20020a630b61000000b00429d91cc649so8822498pgl.8 for ; Tue, 22 Nov 2022 10:10:11 -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=QoqA4TTHtwV1fAtIvj47WssSLUg61SUyeuraqKf8Rhg=; b=1KgvL/zB2bXb5VHEq9EMOZlDSW5RPfY6dAzIy2mltSP5ARysyO/Fjs0xVa4JXtvz2s uPg78ciOmcDOknGeXl5fH4wzP1m+5xXnSdlqwhDsK2sJikO4M9xW3sSKVi0S9xqFdaKu 3L0FAs5yMe3zsm429Vre3SZiUM8bh+tb5ZJzDEUwWn9Wuo6iiAHNZHWgfbNWlsK8Bwm3 Brf1+Pl3pJZWhyVwPvFUib88wwT75w7VICvcapQ1Zq146Ki5Ku4U5famO4aRyMa+D2Rw SkiQno7RRxyJCF0zery/YaKsTMW4cjjaCNDE/1uoc4hwLV6CnhaSu5U21TY/f01Pq02p Uqtw== X-Gm-Message-State: ANoB5pkt1ucBC7PC0vZqxs+hjb+TfLdOrRXB9PeymeokFR1vkH1XzmCA CYEnnHnwrkLNHbKUuNykxprK4hhsnLAE3yuYjgRXhnBoeCA58H++XFt/1apfQAaEx5ikkRn6r6C DhDBxZzw+dLqfAaRW8LQUZ0eE X-Received: by 2002:a17:902:bc43:b0:186:da90:5936 with SMTP id t3-20020a170902bc4300b00186da905936mr5602624plz.158.1669140609803; Tue, 22 Nov 2022 10:10:09 -0800 (PST) X-Google-Smtp-Source: AA0mqf5DJmmp20Nh7s7ijiFzxnj9TAeP4VP0FdaEYnUeKEOe57lisQyRsX9CrBnFemn7BWAxylkHdQ== X-Received: by 2002:a17:902:bc43:b0:186:da90:5936 with SMTP id t3-20020a170902bc4300b00186da905936mr5602605plz.158.1669140609533; Tue, 22 Nov 2022 10:10:09 -0800 (PST) Received: from localhost ([240d:1a:c0d:9f00:4f2f:926a:23dd:8588]) by smtp.gmail.com with ESMTPSA id y5-20020a636405000000b0046f1cbd2631sm9587265pgb.50.2022.11.22.10.10.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Nov 2022 10:10:09 -0800 (PST) Date: Wed, 23 Nov 2022 03:10:05 +0900 (JST) Message-Id: <20221123.031005.476714651315933198.syoshida@redhat.com> To: edumazet@google.com 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 Subject: Re: [PATCH v2] net: tun: Fix use-after-free in tun_detach() From: Shigeru Yoshida In-Reply-To: References: <20221120090213.922567-1-syoshida@redhat.com> X-Mailer: Mew version 6.8 on Emacs 28.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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...). Thanks, Shigeru > > Thanks. > >> + synchronize_rcu(); >> + sock_put(&tfile->sk); >> + } >> } >> >> static void tun_detach_all(struct net_device *dev) >> -- >> 2.38.1 >> >