======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.25/4431 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:
ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline]
ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline]
ffff88805bfac130 (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.0.25/4431:
 #0: ffff88805ae20e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline]
 #0: ffff88805ae20e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:653 [inline]
 #0: ffff88805ae20e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x82/0x210 net/socket.c:1400
 #1: ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #1: ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline]
 #1: ffff88805bfac130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:191 [inline]
 #1: ffff88805bfac130 (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: 4431 Comm: syz.0.25 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 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: 0033:0x7f6076d9e159
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:00007ffc05976fa8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffc05977090 RCX: 00007f6076d9e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000018668 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2d920000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6077025fac R14: 00007f6077025fa8 R15: 00007f6077025fa0
 </TASK>