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 14F83C54EBC for ; Sun, 8 Jan 2023 10:13:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232902AbjAHKM7 (ORCPT ); Sun, 8 Jan 2023 05:12:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229716AbjAHKM6 (ORCPT ); Sun, 8 Jan 2023 05:12:58 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F478DEC1; Sun, 8 Jan 2023 02:12:57 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id CF78BB8072F; Sun, 8 Jan 2023 10:12:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A47F2C433D2; Sun, 8 Jan 2023 10:12:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673172774; bh=aXDvVjDD2m0fpvw0sP14+hXs+4qDt0cRVfRKbtbBPRA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=T2xPeBoAzJfj0kagZLMAH1sDIVnrnZX1RQ10CEtvvzYPjxlHLlRVcYZIxIP+sVHR3 BVe/Dp8VP6wOqJtLGH6h2VVohuaTNzeDUy86tVinv7JDW8J7Xj++pDTmKaLWsKTIdx LDcLArW8R4FiU8R1413GVIjdD6nsL15Ul7i1TJRd0iZIhRhrvF2tFUFEbC2YrHcjUi Pgh2qKCCq3075k7yGApG1Ergoj6d/41QNRBLiOAvbISbT5fn8n1tRg3L5L/vycN9X2 jwoW9xIpHoYmojsvKGdtIB39L6UZDm2XAyUdokwWaYvzwGeiKuymFxIwXoyt9HUM+f Y/z9x6bwkhs8A== Date: Sun, 8 Jan 2023 12:12:49 +0200 From: Leon Romanovsky To: Saeed Mahameed Cc: Ying Hsu , linux-bluetooth@vger.kernel.org, chromeos-bluetooth-upstreaming@chromium.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Johan Hedberg , Luiz Augusto von Dentz , Marcel Holtmann , Paolo Abeni , linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH] Bluetooth: Fix possible deadlock in rfcomm_sk_state_change Message-ID: References: <20230103111221.1.I1f29bb547a03e9adfe2e6754212f9d14a2e39c4b@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jan 05, 2023 at 04:24:10PM -0800, Saeed Mahameed wrote: > On 04 Jan 08:51, Leon Romanovsky wrote: > > On Tue, Jan 03, 2023 at 11:12:46AM +0000, Ying Hsu wrote: > > > There's a possible deadlock when two processes are connecting > > > and closing concurrently: > > > + CPU0: __rfcomm_dlc_close locks rfcomm and then calls > > > rfcomm_sk_state_change which locks the sock. > > > + CPU1: rfcomm_sock_connect locks the socket and then calls > > > rfcomm_dlc_open which locks rfcomm. > > > > > > Here's the call trace: > > > > > > -> #2 (&d->lock){+.+.}-{3:3}: > > > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > > > __mutex_lock0x12f/0x1360 kernel/locking/mutex.c:747 > > > __rfcomm_dlc_close+0x15d/0x890 net/bluetooth/rfcomm/core.c:487 > > > rfcomm_dlc_close+1e9/0x240 net/bluetooth/rfcomm/core.c:520 > > > __rfcomm_sock_close+0x13c/0x250 net/bluetooth/rfcomm/sock.c:220 > > > rfcomm_sock_shutdown+0xd8/0x230 net/bluetooth/rfcomm/sock.c:907 > > > rfcomm_sock_release+0x68/0x140 net/bluetooth/rfcomm/sock.c:928 > > > __sock_release+0xcd/0x280 net/socket.c:650 > > > sock_close+0x1c/0x20 net/socket.c:1365 > > > __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+0xaa8/0x2950 kernel/exit.c:867 > > > do_group_exit+0xd4/0x2a0 kernel/exit.c:1012 > > > get_signal+0x21c3/0x2450 kernel/signal.c:2859 > > > arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306 > > > 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 > > > > > > -> #1 (rfcomm_mutex){+.+.}-{3:3}: > > > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > > > __mutex_lock+0x12f/0x1360 kernel/locking/mutex.c:747 > > > rfcomm_dlc_open+0x93/0xa80 net/bluetooth/rfcomm/core.c:425 > > > rfcomm_sock_connect+0x329/0x450 net/bluetooth/rfcomm/sock.c:413 > > > __sys_connect_file+0x153/0x1a0 net/socket.c:1976 > > > __sys_connect+0x165/0x1a0 net/socket.c:1993 > > > __do_sys_connect net/socket.c:2003 [inline] > > > __se_sys_connect net/socket.c:2000 [inline] > > > __x64_sys_connect+0x73/0xb0 net/socket.c:2000 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > > > > -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}: > > > check_prev_add kernel/locking/lockdep.c:3097 [inline] > > > check_prevs_add kernel/locking/lockdep.c:3216 [inline] > > > validate_chain kernel/locking/lockdep.c:3831 [inline] > > > __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055 > > > lock_acquire kernel/locking/lockdep.c:5668 [inline] > > > lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633 > > > lock_sock_nested+0x3a/0xf0 net/core/sock.c:3470 > > > lock_sock include/net/sock.h:1725 [inline] > > > rfcomm_sk_state_change+0x6d/0x3a0 net/bluetooth/rfcomm/sock.c:73 > > > __rfcomm_dlc_close+0x1b1/0x890 net/bluetooth/rfcomm/core.c:489 > > > rfcomm_dlc_close+0x1e9/0x240 net/bluetooth/rfcomm/core.c:520 > > > __rfcomm_sock_close+0x13c/0x250 net/bluetooth/rfcomm/sock.c:220 > > > rfcomm_sock_shutdown+0xd8/0x230 net/bluetooth/rfcomm/sock.c:907 > > > rfcomm_sock_release+0x68/0x140 net/bluetooth/rfcomm/sock.c:928 > > > __sock_release+0xcd/0x280 net/socket.c:650 > > > sock_close+0x1c/0x20 net/socket.c:1365 > > > __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+0xaa8/0x2950 kernel/exit.c:867 > > > do_group_exit+0xd4/0x2a0 kernel/exit.c:1012 > > > get_signal+0x21c3/0x2450 kernel/signal.c:2859 > > > arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306 > > > 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 > > > > > > Signed-off-by: Ying Hsu > > > --- > > > This commit has been tested with a C reproducer on qemu-x86_64. > > > > > > net/bluetooth/rfcomm/sock.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c > > > index 21e24da4847f..29f9a88a3dc8 100644 > > > --- a/net/bluetooth/rfcomm/sock.c > > > +++ b/net/bluetooth/rfcomm/sock.c > > > @@ -410,8 +410,10 @@ static int rfcomm_sock_connect(struct socket *sock, struct sockaddr *addr, int a > > > d->sec_level = rfcomm_pi(sk)->sec_level; > > > d->role_switch = rfcomm_pi(sk)->role_switch; > > > > > > + release_sock(sk); > > > err = rfcomm_dlc_open(d, &rfcomm_pi(sk)->src, &sa->rc_bdaddr, > > ^^^^ > > Are you sure that "sk" still exists here after you called to release_sock(sk)? > > What prevents from use-after-free here? > > > > sk must be valid to be locked in first place. It is, but after it is released it won't. > release_sock() has mutex unlock semantics so it doesn't free anything.. What do you mean? I see a lot of magic release calls. 3481 void release_sock(struct sock *sk) 3482 { 3483 spin_lock_bh(&sk->sk_lock.slock); 3484 if (sk->sk_backlog.tail) 3485 __release_sock(sk); 3486 3487 /* Warning : release_cb() might need to release sk ownership, 3488 * ie call sock_release_ownership(sk) before us. 3489 */ 3490 if (sk->sk_prot->release_cb) 3491 sk->sk_prot->release_cb(sk); 3492 3493 sock_release_ownership(sk); 3494 if (waitqueue_active(&sk->sk_lock.wq)) 3495 wake_up(&sk->sk_lock.wq); 3496 spin_unlock_bh(&sk->sk_lock.slock); 3497 } 3498 EXPORT_SYMBOL(release_sock); Thanks