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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 CA498C4320E for ; Sat, 28 Aug 2021 16:06:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5FF460E93 for ; Sat, 28 Aug 2021 16:06:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234477AbhH1QHg (ORCPT ); Sat, 28 Aug 2021 12:07:36 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:33614 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230290AbhH1QHf (ORCPT ); Sat, 28 Aug 2021 12:07:35 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 65F6B1FFF0; Sat, 28 Aug 2021 16:06:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1630166803; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+hbC3CoQ9GVXH6EUwVQgeUfZ0rKGJOCmzlFVSyEolJ8=; b=kISMPvHHQ6O8y4GUBGL/H/u/F0Zg4JfidpT4awwChegbQm4rSecP9MHT53bxdlNuUfqHN3 5hxsvPpEva673ZNrGGuAEWaGDO6zxIyhZhTSUwOx0ieokZmvFZHGo71dkUDUSwznlff1A8 cPad3NU11BlUccwe7ofiJTvQqbXkzhU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1630166803; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+hbC3CoQ9GVXH6EUwVQgeUfZ0rKGJOCmzlFVSyEolJ8=; b=fmISJ3gxhJnk41FlFazH1RZt4ZDZ8QvP5XEsQCVklpYTXWRol/3L5BhqSadzFaGvQMDrb3 MpbEl6WbJuN6uHAw== Received: from alsa1.suse.de (alsa1.suse.de [10.160.4.42]) by relay2.suse.de (Postfix) with ESMTP id 5FF18A3B88; Sat, 28 Aug 2021 16:06:43 +0000 (UTC) Date: Sat, 28 Aug 2021 18:06:43 +0200 Message-ID: From: Takashi Iwai To: Luiz Augusto von Dentz Cc: "linux-bluetooth@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: CVE-2021-3640 and the unlimited block of lock_sock() In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Aug 2021 03:28:09 +0200, Luiz Augusto von Dentz wrote: > > 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. OK, now I tried a similar way like the commit 92c685dc5de0 to move the memcpy_from_msg() call out of lock_sock(), and it seems working. I'm going to submit the fix. thanks, Takashi