====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.4.22/4464 is trying to acquire lock: ffff800017b9ce88 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_close+0x44/0x198 net/bluetooth/rfcomm/core.c:507 but task is already holding lock: ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline] ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe0/0x2f0 net/bluetooth/rfcomm/sock.c:225 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+0x70/0x130 net/core/sock.c:3504 lock_sock include/net/sock.h:1805 [inline] rfcomm_connect_ind+0x49c/0xb6c net/bluetooth/rfcomm/sock.c:966 rfcomm_recv_pn net/bluetooth/rfcomm/core.c:1504 [inline] rfcomm_recv_mcc net/bluetooth/rfcomm/core.c:1722 [inline] rfcomm_recv_frame net/bluetooth/rfcomm/core.c:1855 [inline] rfcomm_process_rx net/bluetooth/rfcomm/core.c:2007 [inline] rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2100 [inline] rfcomm_run+0x2290/0x4b50 net/bluetooth/rfcomm/core.c:2188 kthread+0x254/0x2e0 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850 -> #0 (rfcomm_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5676 __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 rfcomm_dlc_close+0x44/0x198 net/bluetooth/rfcomm/core.c:507 __rfcomm_sock_close+0x1c0/0x2f0 net/bluetooth/rfcomm/sock.c:232 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:247 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] __rfcomm_sock_close+0xe8/0x2f0 net/bluetooth/rfcomm/sock.c:225 rfcomm_sock_shutdown+0xa8/0x210 net/bluetooth/rfcomm/sock.c:918 rfcomm_sock_release+0x58/0x118 net/bluetooth/rfcomm/sock.c:939 __sock_release net/socket.c:654 [inline] sock_close+0xac/0x1ec net/socket.c:1400 __fput+0x1b4/0x7b0 fs/file_table.c:320 ____fput+0x20/0x30 fs/file_table.c:348 task_work_run+0x1f4/0x280 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 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 *** 2 locks held by syz.4.22/4464: #0: ffff0000dfeaa010 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline] #0: ffff0000dfeaa010 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: __sock_release net/socket.c:653 [inline] #0: ffff0000dfeaa010 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: sock_close+0x74/0x1ec net/socket.c:1400 #1: ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline] #1: ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] #1: ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] #1: ffff0000d1694130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe0/0x2f0 net/bluetooth/rfcomm/sock.c:225 stack backtrace: CPU: 1 PID: 4464 Comm: syz.4.22 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026 Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5676 __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 rfcomm_dlc_close+0x44/0x198 net/bluetooth/rfcomm/core.c:507 __rfcomm_sock_close+0x1c0/0x2f0 net/bluetooth/rfcomm/sock.c:232 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:247 [inline] rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] __rfcomm_sock_close+0xe8/0x2f0 net/bluetooth/rfcomm/sock.c:225 rfcomm_sock_shutdown+0xa8/0x210 net/bluetooth/rfcomm/sock.c:918 rfcomm_sock_release+0x58/0x118 net/bluetooth/rfcomm/sock.c:939 __sock_release net/socket.c:654 [inline] sock_close+0xac/0x1ec net/socket.c:1400 __fput+0x1b4/0x7b0 fs/file_table.c:320 ____fput+0x20/0x30 fs/file_table.c:348 task_work_run+0x1f4/0x280 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585