====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.1842/10547 is trying to acquire lock: ffff88805fee80b8 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7171 but task is already holding lock: ffffffff8e562248 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (rfcomm_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2214 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2080 hci_encrypt_change_evt+0x6c8/0xe30 net/bluetooth/hci_event.c:3648 hci_event_func net/bluetooth/hci_event.c:7500 [inline] hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 -> #1 (hci_cb_list_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 hci_connect_cfm include/net/bluetooth/hci_core.h:2001 [inline] hci_remote_features_evt+0x535/0x900 net/bluetooth/hci_event.c:3719 hci_event_func net/bluetooth/hci_event.c:7500 [inline] hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 -> #0 (&hdev->lock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7171 l2cap_sock_connect+0x586/0x760 net/bluetooth/l2cap_sock.c:257 kernel_connect+0x142/0x1c0 net/socket.c:3636 rfcomm_session_create net/bluetooth/rfcomm/core.c:811 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline] rfcomm_dlc_open+0xa1f/0xec0 net/bluetooth/rfcomm/core.c:431 rfcomm_sock_connect+0x2ed/0x600 net/bluetooth/rfcomm/sock.c:421 __sys_connect_file net/socket.c:2057 [inline] __sys_connect+0x3da/0x470 net/socket.c:2074 __do_sys_connect net/socket.c:2084 [inline] __se_sys_connect net/socket.c:2081 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2081 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 other info that might help us debug this: Chain exists of: &hdev->lock --> hci_cb_list_lock --> rfcomm_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rfcomm_mutex); lock(hci_cb_list_lock); lock(rfcomm_mutex); lock(&hdev->lock); *** DEADLOCK *** 1 lock held by syz.0.1842/10547: #0: ffffffff8e562248 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429 stack backtrace: CPU: 1 PID: 10547 Comm: syz.0.1842 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7171 l2cap_sock_connect+0x586/0x760 net/bluetooth/l2cap_sock.c:257 kernel_connect+0x142/0x1c0 net/socket.c:3636 rfcomm_session_create net/bluetooth/rfcomm/core.c:811 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline] rfcomm_dlc_open+0xa1f/0xec0 net/bluetooth/rfcomm/core.c:431 rfcomm_sock_connect+0x2ed/0x600 net/bluetooth/rfcomm/sock.c:421 __sys_connect_file net/socket.c:2057 [inline] __sys_connect+0x3da/0x470 net/socket.c:2074 __do_sys_connect net/socket.c:2084 [inline] __se_sys_connect net/socket.c:2081 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2081 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fbee219e159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fbee311d028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007fbee2425fa0 RCX: 00007fbee219e159 RDX: 0000000000000011 RSI: 0000200000000040 RDI: 0000000000000004 RBP: 00007fbee223503b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fbee2426038 R14: 00007fbee2425fa0 R15: 00007ffcf2235368