From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f70.google.com (mail-ot1-f70.google.com [209.85.210.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 69C313624C3 for ; Fri, 2 Oct 2026 06:15:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790921737; cv=none; b=rinMdPCv5LR8uWRpzPCePqQje75qSp+mxkciMXbsTF1UuWrIcpv0eWp/xGPNhLWr8eYGlGONiU3GHFCPV4p5rLBu5BnZUsWyD+K9Qo/NiMOutH1vNHoVehoyI+HyPpd7cEVj31tZnkxzYWYx7572F3kkG6hZRof3AMeC+B93wDg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790921737; c=relaxed/simple; bh=cCWTomR+IxE8n110azN/buoa+QOBIeOrS7DImRQP20I=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=Q0Q/mtsFvmGhrRtrw6i+KlyIfE1n5z3s++iUzMe41RgtTEIXaEJUGpYc0XtYOBcFCMf/0ZYVeMFXc/Fk2PndXR63Rhb6IeqKO8XXMl8XbGz0W5jumwz/lA8UtVDrwHxmNwhdGFgp727ElwdNglOMdTmueDckIFCtJqhVjCn9RLY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.210.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-ot1-f70.google.com with SMTP id 46e09a7af769-82315dbce25so134759a34.2 for ; Thu, 01 Oct 2026 23:15:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790921734; x=1791526534; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=VHl164KF9QmUiHMYC+0V/c2CfiNGjgIdO8kbSXlbTVs=; b=E0sRu5U7V3Gyr26ISs85+Z4pZKi2com20dcZPzO7gh88QRAZl0mDlEBC8Lrsm5kkrZ Ga4Fd9Q/1tgkixbV14AhMnPNK0jHyPti9csrPmGg6QP1BDGz9zxcDL79qhQaWHysPFM+ OtFyXyCdeZ6kYAC+3eGV34KwmpLDN4MhGDhxoctJ7F8wwSiTRml+jUp737XJZBeqg0zU IIDpMCKKX+daFyz6z/xnfRbh9oC48PxfnvOVcwhgIm1jaSAargEIAn8CbVZ0+9qfRRn+ ipZ0JHJlmLVmRhcxtuLDjwkznF04iGTNmlz1OJSL7DXeVajGyYF0yPFhI1qlzwx5tyxI FsYA== X-Forwarded-Encrypted: i=1; AKwUvBxSK4FAltmkNk0UNUxPGgcs7ZLWezzeo0uE2zhGXZh/3ak/mFRIMHNZQucaU55TzHIyt5QGx/EksMGFrgQ=@vger.kernel.org X-Gm-Message-State: AFuF++nyEt6mr3f7WjJrt28iQsbOmHwhU3YIus2SaS8aHugQ8kV1CMTg Ytp0JKsZ/BcrjV5JKwAzL8FWhKBRj1ojosfJtbjyysMgbfqU4Hy6AmGsJYMN+LpyFMAHvEK5s2o xTFWzcgLBj8i8jFvNXXdqlVyuNMAnMDZy8VNiZgLUiuSyIXhRDFYdP+l4WF8= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:1315:b0:4e6:76eb:b997 with SMTP id 5614622812f47-4f52a5776f4mr1201120b6e.62.1790921734140; Thu, 01 Oct 2026 23:15:34 -0700 (PDT) Date: Thu, 01 Oct 2026 23:15:34 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6abf4c06.9b478af7.e8d7a.0007.GAE@google.com> Subject: [syzbot] [bluetooth?] possible deadlock in rfcomm_run From: syzbot To: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, luiz.dentz@gmail.com, marcel@holtmann.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: d266640c6c76 Merge tag 'driver-core-7.3-rc5' of git://git... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1586b315580000 kernel config: https://syzkaller.appspot.com/x/.config?x=7d012d9c67977ee4 dashboard link: https://syzkaller.appspot.com/bug?extid=0adf2aef8ca78b84c4df compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-d266640c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/b8d2ccf5a23e/vmlinux-d266640c.xz kernel image: https://storage.googleapis.com/syzbot-assets/0b1dbd9ea9d5/bzImage-d266640c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0adf2aef8ca78b84c4df@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ krfcommd/3367 is trying to acquire lock: ffff888062feb940 ((wq_completion)hci3){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x9c/0x1c0 kernel/workqueue.c:4111 but task is already holding lock: ffffffff90f83cc0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2096 [inline] ffffffff90f83cc0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_run+0x30b/0x5550 net/bluetooth/rfcomm/core.c:2205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (rfcomm_mutex){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 rfcomm_dlc_open+0x92/0xac0 net/bluetooth/rfcomm/core.c:426 rfcomm_dev_activate+0x83/0x110 net/bluetooth/rfcomm/tty.c:112 tty_port_open+0x156/0x1f0 drivers/tty/tty_port.c:769 rfcomm_tty_open+0xad/0x490 net/bluetooth/rfcomm/tty.c:745 tty_open+0x2cc/0xe20 drivers/tty/tty_io.c:2110 chrdev_open+0x234/0x6a0 fs/char_dev.c:411 do_dentry_open+0x6ab/0x14d0 fs/open.c:996 vfs_open+0x82/0x3f0 fs/open.c:1101 do_open fs/namei.c:4837 [inline] path_openat+0x19fa/0x2440 fs/namei.c:5000 do_file_open+0x20e/0x430 fs/namei.c:5029 do_sys_openat2+0x10f/0x1e0 fs/open.c:1417 do_sys_open fs/open.c:1423 [inline] __do_sys_open fs/open.c:1431 [inline] __se_sys_open fs/open.c:1427 [inline] __x64_sys_open+0xfe/0x1d0 fs/open.c:1427 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&port->mutex){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 class_mutex_constructor include/linux/mutex.h:253 [inline] uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1646 tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341 set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516 tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803 n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982 n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496 tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2774 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (&tty->termios_rwsem){++++}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline] n_tty_flush_buffer+0x25/0x1b0 drivers/tty/n_tty.c:349 tty_buffer_flush+0x239/0x310 drivers/tty/tty_buffer.c:248 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 tty_port_close_start+0x306/0x500 drivers/tty/tty_port.c:648 tty_port_close+0x26/0x170 drivers/tty/tty_port.c:703 tty_release+0x40e/0x1300 drivers/tty/tty_io.c:1718 __fput+0x3ff/0xb50 fs/file_table.c:512 task_work_run+0x150/0x240 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:70 [inline] exit_to_user_mode_loop+0x1d8/0x700 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline] do_syscall_64+0x661/0x790 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&buf->lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236 tty_ldisc_flush+0xad/0xf0 drivers/tty/tty_ldisc.c:388 hci_uart_flush+0xed/0x630 drivers/bluetooth/hci_ldisc.c:255 hci_uart_close+0x1d/0x90 drivers/bluetooth/hci_ldisc.c:292 hci_dev_open_sync+0x126f/0x25e0 net/bluetooth/hci_sync.c:5480 hci_dev_do_open+0x2a/0xb0 net/bluetooth/hci_core.c:431 hci_power_on+0x131/0x630 net/bluetooth/hci_core.c:923 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&hdev->req_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 hci_dev_do_open+0x22/0xb0 net/bluetooth/hci_core.c:429 hci_power_on+0x131/0x630 net/bluetooth/hci_core.c:923 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((work_completion)(&hdev->power_on)){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 process_one_work+0xa32/0x1b10 kernel/workqueue.c:3372 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((wq_completion)hci3){+.+.}-{0:0}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4111 __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4153 drain_workqueue+0x175/0x3b0 kernel/workqueue.c:4317 destroy_workqueue+0xc3/0xa30 kernel/workqueue.c:6155 hci_release_dev+0x14d/0x630 net/bluetooth/hci_core.c:2717 bt_host_release+0x6b/0xb0 net/bluetooth/hci_sysfs.c:100 device_release+0xd2/0x270 drivers/base/core.c:2640 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1f7/0x640 lib/kobject.c:737 put_device+0x1f/0x30 drivers/base/core.c:3884 device_release+0xd2/0x270 drivers/base/core.c:2640 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1f7/0x640 lib/kobject.c:737 put_device+0x1f/0x30 drivers/base/core.c:3884 hci_conn_put include/net/bluetooth/hci_core.h:1689 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1856 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1869 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:494 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x352/0x3f0 net/bluetooth/l2cap_core.c:521 l2cap_sock_release+0x1db/0x280 net/bluetooth/l2cap_sock.c:1533 __sock_release net/socket.c:735 [inline] sock_release+0x91/0x1c0 net/socket.c:763 rfcomm_session_del.isra.0+0x16b/0x250 net/bluetooth/rfcomm/core.c:718 rfcomm_process_rx net/bluetooth/rfcomm/core.c:2030 [inline] rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2115 [inline] rfcomm_run+0x6f6/0x5550 net/bluetooth/rfcomm/core.c:2205 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: (wq_completion)hci3 --> &port->mutex --> rfcomm_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rfcomm_mutex); lock(&port->mutex); lock(rfcomm_mutex); lock((wq_completion)hci3); *** DEADLOCK *** locks held by krfcommd/3367: 1, last CPU#1: #0: ffffffff90f83cc0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2096 [inline] #0: ffffffff90f83cc0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_run+0x30b/0x5550 net/bluetooth/rfcomm/core.c:2205 stack backtrace: CPU: 1 UID: 0 PID: 3367 Comm: krfcommd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4111 __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4153 drain_workqueue+0x175/0x3b0 kernel/workqueue.c:4317 destroy_workqueue+0xc3/0xa30 kernel/workqueue.c:6155 hci_release_dev+0x14d/0x630 net/bluetooth/hci_core.c:2717 bt_host_release+0x6b/0xb0 net/bluetooth/hci_sysfs.c:100 device_release+0xd2/0x270 drivers/base/core.c:2640 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1f7/0x640 lib/kobject.c:737 put_device+0x1f/0x30 drivers/base/core.c:3884 device_release+0xd2/0x270 drivers/base/core.c:2640 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1f7/0x640 lib/kobject.c:737 put_device+0x1f/0x30 drivers/base/core.c:3884 hci_conn_put include/net/bluetooth/hci_core.h:1689 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1856 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1869 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:494 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x352/0x3f0 net/bluetooth/l2cap_core.c:521 l2cap_sock_release+0x1db/0x280 net/bluetooth/l2cap_sock.c:1533 __sock_release net/socket.c:735 [inline] sock_release+0x91/0x1c0 net/socket.c:763 rfcomm_session_del.isra.0+0x16b/0x250 net/bluetooth/rfcomm/core.c:718 rfcomm_process_rx net/bluetooth/rfcomm/core.c:2030 [inline] rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2115 [inline] rfcomm_run+0x6f6/0x5550 net/bluetooth/rfcomm/core.c:2205 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup