====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.4.5/4379 is trying to acquire lock: ffffffff8dedcb88 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_close+0x35/0x180 net/bluetooth/rfcomm/core.c:507 but task is already holding lock: ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline] ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xd5/0x2b0 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+0x44/0x100 net/core/sock.c:3504 lock_sock include/net/sock.h:1805 [inline] rfcomm_connect_ind+0x4ec/0xd80 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+0x2ac7/0x5d70 net/bluetooth/rfcomm/core.c:2188 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #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+0x2d18/0x7c40 kernel/locking/lockdep.c:5063 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747 rfcomm_dlc_close+0x35/0x180 net/bluetooth/rfcomm/core.c:507 __rfcomm_sock_close+0x18a/0x2b0 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+0xdd/0x2b0 net/bluetooth/rfcomm/sock.c:225 rfcomm_sock_shutdown+0xb5/0x240 net/bluetooth/rfcomm/sock.c:918 rfcomm_sock_release+0x55/0x110 net/bluetooth/rfcomm/sock.c:939 __sock_release net/socket.c:654 [inline] sock_close+0xbf/0x210 net/socket.c:1400 __fput+0x20a/0x8b0 fs/file_table.c:320 task_work_run+0x1d0/0x260 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 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.4.5/4379: #0: ffff888056205610 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline] #0: ffff888056205610 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:653 [inline] #0: ffff888056205610 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x82/0x210 net/socket.c:1400 #1: ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline] #1: ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline] #1: ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline] #1: ffff88807d21b130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xd5/0x2b0 net/bluetooth/rfcomm/sock.c:225 stack backtrace: CPU: 0 PID: 4379 Comm: syz.4.5 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106 check_noncircular+0x296/0x330 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+0x2d18/0x7c40 kernel/locking/lockdep.c:5063 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747 rfcomm_dlc_close+0x35/0x180 net/bluetooth/rfcomm/core.c:507 __rfcomm_sock_close+0x18a/0x2b0 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+0xdd/0x2b0 net/bluetooth/rfcomm/sock.c:225 rfcomm_sock_shutdown+0xb5/0x240 net/bluetooth/rfcomm/sock.c:918 rfcomm_sock_release+0x55/0x110 net/bluetooth/rfcomm/sock.c:939 __sock_release net/socket.c:654 [inline] sock_close+0xbf/0x210 net/socket.c:1400 __fput+0x20a/0x8b0 fs/file_table.c:320 task_work_run+0x1d0/0x260 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f1b71b9e159 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:00007fff04c43218 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007fff04c43300 RCX: 00007f1b71b9e159 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 0000000000015fdd R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b2ef20000 R11: 0000000000000246 R12: 00007fff04c43340 R13: 00007f1b71e25fac R14: 0000000000016024 R15: 00007f1b71e25fa0