====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.355/6556 is trying to acquire lock: ffff80008a06cbe0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_close+0x44/0x1cc net/bluetooth/rfcomm/core.c:508 but task is already holding lock: ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline] ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe0/0x330 net/bluetooth/rfcomm/sock.c:224 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}: lock_sock_nested+0x58/0x110 net/core/sock.c:3827 lock_sock include/net/sock.h:1713 [inline] rfcomm_connect_ind+0x498/0x920 net/bluetooth/rfcomm/sock.c:968 rfcomm_recv_pn net/bluetooth/rfcomm/core.c:1509 [inline] rfcomm_recv_mcc net/bluetooth/rfcomm/core.c:1727 [inline] rfcomm_recv_frame net/bluetooth/rfcomm/core.c:1868 [inline] rfcomm_process_rx net/bluetooth/rfcomm/core.c:2020 [inline] rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2114 [inline] rfcomm_run+0x1f08/0x4bac net/bluetooth/rfcomm/core.c:2204 kthread+0x304/0x3d4 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838 -> #0 (rfcomm_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1600/0x2a6c kernel/locking/lockdep.c:5254 lock_acquire+0x150/0x370 kernel/locking/lockdep.c:5908 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0xf14 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 rfcomm_dlc_close+0x44/0x1cc net/bluetooth/rfcomm/core.c:508 __rfcomm_sock_close+0x1c0/0x330 net/bluetooth/rfcomm/sock.c:231 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] __rfcomm_sock_close+0xe8/0x330 net/bluetooth/rfcomm/sock.c:224 rfcomm_sock_shutdown+0xa8/0x23c net/bluetooth/rfcomm/sock.c:920 rfcomm_sock_release+0x58/0x160 net/bluetooth/rfcomm/sock.c:941 __sock_release+0xa0/0x1d4 net/socket.c:735 sock_close+0x24/0x38 net/socket.c:1526 __fput+0x338/0x74c fs/file_table.c:512 ____fput+0x20/0x30 fs/file_table.c:540 task_work_run+0x1cc/0x25c 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+0x10c/0x17c 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] arm64_syscall_exit_to_user_mode arch/arm64/kernel/entry-common.c:108 [inline] el0_svc+0x18c/0x260 arch/arm64/kernel/entry-common.c:759 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM); lock(rfcomm_mutex); lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM); lock(rfcomm_mutex); *** DEADLOCK *** locks held by syz.3.355/6556: 2, last CPU#1: #0: ffff0000f3539380 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline] #0: ffff0000f3539380 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: __sock_release+0x7c/0x1d4 net/socket.c:734 #1: ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] #1: ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline] #1: ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] #1: ffff0000d4314260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe0/0x330 net/bluetooth/rfcomm/sock.c:224 stack backtrace: CPU: 1 UID: 0 PID: 6556 Comm: syz.3.355 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x328/0x330 kernel/locking/lockdep.c:2059 check_noncircular+0x158/0x174 kernel/locking/lockdep.c:2191 check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1600/0x2a6c kernel/locking/lockdep.c:5254 lock_acquire+0x150/0x370 kernel/locking/lockdep.c:5908 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0xf14 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 rfcomm_dlc_close+0x44/0x1cc net/bluetooth/rfcomm/core.c:508 __rfcomm_sock_close+0x1c0/0x330 net/bluetooth/rfcomm/sock.c:231 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline] __rfcomm_sock_close+0xe8/0x330 net/bluetooth/rfcomm/sock.c:224 rfcomm_sock_shutdown+0xa8/0x23c net/bluetooth/rfcomm/sock.c:920 rfcomm_sock_release+0x58/0x160 net/bluetooth/rfcomm/sock.c:941 __sock_release+0xa0/0x1d4 net/socket.c:735 sock_close+0x24/0x38 net/socket.c:1526 __fput+0x338/0x74c fs/file_table.c:512 ____fput+0x20/0x30 fs/file_table.c:540 task_work_run+0x1cc/0x25c 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+0x10c/0x17c 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] arm64_syscall_exit_to_user_mode arch/arm64/kernel/entry-common.c:108 [inline] el0_svc+0x18c/0x260 arch/arm64/kernel/entry-common.c:759 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590