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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,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 66900C4320A for ; Fri, 27 Aug 2021 01:28:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F52160F45 for ; Fri, 27 Aug 2021 01:28:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243928AbhH0B3L (ORCPT ); Thu, 26 Aug 2021 21:29:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243894AbhH0B3J (ORCPT ); Thu, 26 Aug 2021 21:29:09 -0400 Received: from mail-vs1-xe36.google.com (mail-vs1-xe36.google.com [IPv6:2607:f8b0:4864:20::e36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 01A42C061757; Thu, 26 Aug 2021 18:28:20 -0700 (PDT) Received: by mail-vs1-xe36.google.com with SMTP id e9so3447719vst.6; Thu, 26 Aug 2021 18:28:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=eojL+CWYVkbXeDacbojpALaYys7Gf6X7mCAj9i6PgeY=; b=XIHjwB7yhPrtlB0C4InUgaZWjxpYRSVVIc27vDUVU65q4gu9fduks6wBc3kr7onySw NMFdLlgtH9bLy/VSYY6HmHHA1C9jBe03g6tQy5hWSO5VJUn3Uu6vSQVs5NxG2plJTdt/ tthZ8aFnrwrUDpRqkTHHK8Jz4RZmXD2E6TyL5EL4djeAu9NEcBs2+0IgnT8bRysYAkbz DF7MiELE4D9E5z9lpOzGOnHlZP/z4wltx+tzAtJOH5rz3tEOcnOXmjo6PpgVC4jeK1wQ U69y1828em49SAc7+608LVXCiZZ2PjS3aQLMxnF2yoX/+9KyIN3vth99y2S8CflVoDV5 plGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=eojL+CWYVkbXeDacbojpALaYys7Gf6X7mCAj9i6PgeY=; b=Zlj7YOnmVuKdhz9LEsO3nFnc6cxBMBYpU/1ECTE75DBbQTKYIqrRQMm3ZAX9hc+wxi ZctugvQLvWbamBRhLWvr2W6TKYnN9QROaw0TxnFom1E1AHKXfCexhLupKrG1f5YnZQZD MCeFnjq7QqTlVzqyvjQZ/PnKpQdxq9Fw162mOIjuOLDgzenw2imSyBQm0+a8ck5Jm/yW lO8qZ+FMO9BtrvCmoVv/KyM5ODrqlqiIuowD8M1dWaRBR8FUG5s2ROZ+FmekhM3xGfC0 tlE52QrdFybF1LAsW7TZhZ9KQP4opf90CNYV8k+mH9h+0kl9sjgPFNtGwpv+gfrILI91 8USQ== X-Gm-Message-State: AOAM533/i5xIP/MlUWrqli77utPkvCiTngRzo3xPQnXdjCFXSkXkdu+R tTeOO2G4wF4yb4kg3nZo8zrcesNohKg1imstv6buFYDk X-Google-Smtp-Source: ABdhPJybVLyee+lXB4edK51zGY1t+HPu1iQFjYuk4eoCiOaxNrdHKe+HbDvG6EJHRBw0fcAEma/dfbrw5ozczWRfyrk= X-Received: by 2002:a67:fa19:: with SMTP id i25mr5426127vsq.7.1630027699947; Thu, 26 Aug 2021 18:28:19 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Luiz Augusto von Dentz Date: Thu, 26 Aug 2021 18:28:09 -0700 Message-ID: Subject: Re: CVE-2021-3640 and the unlimited block of lock_sock() To: Takashi Iwai Cc: "linux-bluetooth@vger.kernel.org" , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Takashi, On Thu, Aug 26, 2021 at 3:29 AM Takashi Iwai wrote: > > On Thu, 19 Aug 2021 17:46:39 +0200, > Takashi Iwai wrote: > > > > Hi, > > > > it seems that the recent fixes in bluetooth tree address most of > > issues in CVE-2021-3640 ("Use-After-Free vulnerability in function > > sco_sock_sendmsg()"). But there is still a problem left: although we > > cover the race with lock_sock() now, the lock may be blocked endlessly > > (as the task takes over with userfaultd), which result in the trigger > > of watchdog like: > > > > -- 8< -- > > [ 23.226767][ T7] Bluetooth: hci0: command 0x0419 tx timeout > > [ 284.985881][ T1529] INFO: task poc:7603 blocked for more than 143 seconds. > > [ 284.989134][ T1529] Not tainted 5.13.0-rc4+ #48 > > [ 284.990098][ T1529] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > [ 284.991705][ T1529] task:poc state:D stack:13784 pid: 7603 ppid: 7593 flags:0x00000000 > > [ 284.993414][ T1529] Call Trace: > > [ 284.994025][ T1529] __schedule+0x32e/0xb90 > > [ 284.994842][ T1529] ? __local_bh_enable_ip+0x72/0xe0 > > [ 284.995987][ T1529] schedule+0x38/0xe0 > > [ 284.996723][ T1529] __lock_sock+0xa1/0x130 > > [ 284.997434][ T1529] ? finish_wait+0x80/0x80 > > [ 284.998150][ T1529] lock_sock_nested+0x9f/0xb0 > > [ 284.998914][ T1529] sco_conn_del+0xb1/0x1a0 > > [ 284.999619][ T1529] ? sco_conn_del+0x1a0/0x1a0 > > [ 285.000361][ T1529] sco_disconn_cfm+0x3a/0x60 > > [ 285.001116][ T1529] hci_conn_hash_flush+0x95/0x130 > > [ 285.001921][ T1529] hci_dev_do_close+0x298/0x680 > > [ 285.002687][ T1529] ? up_write+0x12/0x130 > > [ 285.003367][ T1529] ? vhci_close_dev+0x20/0x20 > > [ 285.004107][ T1529] hci_unregister_dev+0x9f/0x240 > > [ 285.004886][ T1529] vhci_release+0x35/0x70 > > [ 285.005602][ T1529] __fput+0xdf/0x360 > > [ 285.006225][ T1529] task_work_run+0x86/0xd0 > > [ 285.006927][ T1529] exit_to_user_mode_prepare+0x267/0x270 > > [ 285.007824][ T1529] syscall_exit_to_user_mode+0x19/0x60 > > [ 285.008694][ T1529] do_syscall_64+0x42/0xa0 > > [ 285.009393][ T1529] entry_SYSCALL_64_after_hwframe+0x44/0xae > > [ 285.010321][ T1529] RIP: 0033:0x4065c7 > > -- 8< -- > > > > Is there any plan to address this? > > > > As a quick hack, I confirmed a workaround like below: > > > > -- 8< -- > > --- a/net/core/sock.c > > +++ b/net/core/sock.c > > @@ -2628,7 +2628,7 @@ void __lock_sock(struct sock *sk) > > prepare_to_wait_exclusive(&sk->sk_lock.wq, &wait, > > TASK_UNINTERRUPTIBLE); > > spin_unlock_bh(&sk->sk_lock.slock); > > - schedule(); > > + schedule_timeout(msecs_to_jiffies(10 * 1000)); > > spin_lock_bh(&sk->sk_lock.slock); > > if (!sock_owned_by_user(sk)) > > break; > > -- 8< -- > > > > .... but I'm not sure whether it's the right way to go. > > Does anyone has an idea? It seems that we need to rework some code so the functions affected by userfaultfd are not used with sock_lock held. -- Luiz Augusto von Dentz