From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (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 9C40E32C942 for ; Thu, 15 Oct 2026 03:45:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792035951; cv=none; b=HrXWikthEX5m8pN9+DhpRiBCdXQUsqZBB1357clS9aVUJRVQnmMK6V9EH977CSGjCewyhE/q8Z1XHZ1oau47Spfwt93/RBFQIkxCDtkMK76f5knVD5N9aG5/zQwbCtEM8X/NIohJ/XsLRTc4P/D8cxXjmTr6b7hJIPIoSXhRkFU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792035951; c=relaxed/simple; bh=iPTfV/w0bH2qLEAQognyuRqxiEnHwgSvJDziKn/eQ5c=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=VMANTJu0qdA0Lnj180XGrR588iNUoaIyDymLeza+kYiYeEeFm0CpwYGKka0ur8SWVgkIqjhZkTb5lFZXNUIyFSbNI9J3x2pcoHAWAghGW/wWxv04jwoflbvC+Q31S8tpRSpiQOp98liciBpuCl5n+FjuZcEnqYG1QxCIw3FJp4g= 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=209.85.167.200 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-oi1-f200.google.com with SMTP id 5614622812f47-4ea2c058e67so1569138b6e.1 for ; Wed, 14 Oct 2026 20:45:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792035948; x=1792640748; 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=/LDGSw/XVEaz9C8NJAHSXkAmYPuQKpJmpFf6V9pdZpA=; b=uiVJgbNpzj1d10noesDrjOIIITf2NmhEuOhxcg0S8Jmp/C8W0aMYFoLG4zcKWEjB/E 2lolTKmq80y/cqMu10QXjI9/WUODp2GXOarZNq2UnILPS5tUX2/6gcgfV2MknVWxNR/q AFgFBiIp+WqJBEk/TS43k87CLbfeWyfiVJXO6LrfN+Vr4ErVfn6GU26bggHyYNOOWoJP nSmua8uyltK6HGlFKSfoPJT1EDePAs+WovNCfCJtU5UsEivJT6Q3exafVnDFSlpzxWmt z+oEQ7iVu0J1pMLODv+bIQAl+9sI7fHk93MRt5XInARFq1hORcTk3I80z8nMkgbKSqPk 1Qng== X-Gm-Message-State: AFq9FYJPFOW1T97vXomgCn3ILJnw5ZgMpZnolFeDXaVADj6JlI0IxK8H MlRa01ITDJiSkCoLNXSotA65NULqsQepIFJnA2sOUN7m/+HJIDyBNISyJqipD78Za2lJ2ZqpvHS /USUeOb8JEiT1sKBT3P7NoD9cR1wE6S6rS9Fmg8iU6iq3VLA5XtW2HjVe2MA= Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:3094:b0:4d6:90d3:e183 with SMTP id 5614622812f47-50c57b67e0emr14242515b6e.44.1792035948521; Wed, 14 Oct 2026 20:45:48 -0700 (PDT) Date: Wed, 14 Oct 2026 20:45:48 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ad04c6c.a150a118.27e199.006b.GAE@google.com> Subject: [syzbot] [bluetooth?] possible deadlock in rfcomm_process_sessions 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: 4eb2586bd40d Add linux-next specific files for 20261012 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1646563e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=76b7c5acaea2288c dashboard link: https://syzkaller.appspot.com/bug?extid=c8793045f4776ea20bc6 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/9d38ae66aa67/disk-4eb2586b.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/033558801021/vmlinux-4eb2586b.xz kernel image: https://storage.googleapis.com/syzbot-assets/7219b4b1459d/bzImage-4eb2586b.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+c8793045f4776ea20bc6@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ krfcommd/3206 is trying to acquire lock: ffff888037d3d948 ((wq_completion)hci2#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0xb5/0x180 kernel/workqueue.c:4272 but task is already holding lock: ffffffff91825f00 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions+0x2c6/0x9690 net/bluetooth/rfcomm/core.c:2150 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (rfcomm_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 rfcomm_security_cfm+0x90/0x820 net/bluetooth/rfcomm/core.c:2277 hci_auth_cfm include/net/bluetooth/hci_core.h:2250 [inline] hci_auth_complete_evt+0x39f/0xc80 net/bluetooth/hci_event.c:3635 hci_event_func net/bluetooth/hci_event.c:8021 [inline] hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8072 hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4124 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (hci_cb_list_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 hci_connect_cfm include/net/bluetooth/hci_core.h:2211 [inline] hci_remote_features_evt+0x53d/0x950 net/bluetooth/hci_event.c:3892 hci_event_func net/bluetooth/hci_event.c:8021 [inline] hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8072 hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4124 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&hdev->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 hci_send_cmd_sync net/bluetooth/hci_core.c:4163 [inline] hci_cmd_work+0xa0/0x850 net/bluetooth/hci_core.c:4212 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((work_completion)(&hdev->cmd_work)){+.+.}-{0:0}: process_one_work kernel/workqueue.c:3471 [inline] process_scheduled_works+0xc03/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((wq_completion)hci2#2){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4272 __flush_workqueue+0x148/0x10b0 kernel/workqueue.c:4314 drain_workqueue+0xce/0x380 kernel/workqueue.c:4478 destroy_workqueue+0xbe/0x7b0 kernel/workqueue.c:6372 hci_release_dev+0xe3/0x1510 net/bluetooth/hci_core.c:2728 bt_host_release+0x93/0xa0 net/bluetooth/hci_sysfs.c:100 device_release+0xc4/0x1f0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x222/0x550 lib/kobject.c:737 device_release+0xc4/0x1f0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x222/0x550 lib/kobject.c:737 hci_conn_put include/net/bluetooth/hci_core.h:1737 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1933 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1946 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:495 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1fd/0x350 net/bluetooth/l2cap_core.c:522 l2cap_sock_release+0x1a2/0x230 net/bluetooth/l2cap_sock.c:1536 __sock_release net/socket.c:735 [inline] sock_release+0x85/0x150 net/socket.c:763 rfcomm_session_del+0x14b/0x270 net/bluetooth/rfcomm/core.c:782 rfcomm_process_sessions+0x7456/0x9690 net/bluetooth/rfcomm/core.c:-1 rfcomm_run+0x3f5/0x620 net/bluetooth/rfcomm/core.c:2259 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 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)hci2#2 --> hci_cb_list_lock --> rfcomm_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rfcomm_mutex); lock(hci_cb_list_lock); lock(rfcomm_mutex); lock((wq_completion)hci2#2); *** DEADLOCK *** locks held by krfcommd/3206: 1, last CPU#1: #0: ffffffff91825f00 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions+0x2c6/0x9690 net/bluetooth/rfcomm/core.c:2150 stack backtrace: CPU: 1 UID: 0 PID: 3206 Comm: krfcommd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4272 __flush_workqueue+0x148/0x10b0 kernel/workqueue.c:4314 drain_workqueue+0xce/0x380 kernel/workqueue.c:4478 destroy_workqueue+0xbe/0x7b0 kernel/workqueue.c:6372 hci_release_dev+0xe3/0x1510 net/bluetooth/hci_core.c:2728 bt_host_release+0x93/0xa0 net/bluetooth/hci_sysfs.c:100 device_release+0xc4/0x1f0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x222/0x550 lib/kobject.c:737 device_release+0xc4/0x1f0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x222/0x550 lib/kobject.c:737 hci_conn_put include/net/bluetooth/hci_core.h:1737 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1933 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1946 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:495 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1fd/0x350 net/bluetooth/l2cap_core.c:522 l2cap_sock_release+0x1a2/0x230 net/bluetooth/l2cap_sock.c:1536 __sock_release net/socket.c:735 [inline] sock_release+0x85/0x150 net/socket.c:763 rfcomm_session_del+0x14b/0x270 net/bluetooth/rfcomm/core.c:782 rfcomm_process_sessions+0x7456/0x9690 net/bluetooth/rfcomm/core.c:-1 rfcomm_run+0x3f5/0x620 net/bluetooth/rfcomm/core.c:2259 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 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. 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