======================================================
WARNING: possible circular locking dependency detected
5.14.0-syzkaller #0 Not tainted
------------------------------------------------------
krfcommd/2873 is trying to acquire lock:
ffff888018852120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]
ffff888018852120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0xb4/0x390 net/bluetooth/rfcomm/sock.c:73

but task is already holding lock:
ffff88807cfe0928 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x162/0x8a0 net/bluetooth/rfcomm/core.c:487

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&d->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       __rfcomm_dlc_close+0x162/0x8a0 net/bluetooth/rfcomm/core.c:487
       rfcomm_process_dlcs net/bluetooth/rfcomm/core.c:1844 [inline]
       rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2003 [inline]
       rfcomm_run+0xf1e/0x4a20 net/bluetooth/rfcomm/core.c:2086
       kthread+0x3e5/0x4d0 kernel/kthread.c:319
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #1 (rfcomm_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       rfcomm_dlc_open+0x8f/0xa80 net/bluetooth/rfcomm/core.c:425
       rfcomm_sock_connect+0x32f/0x460 net/bluetooth/rfcomm/sock.c:413
       __sys_connect_file+0x155/0x1a0 net/socket.c:1896
       __sys_connect+0x161/0x190 net/socket.c:1913
       __do_sys_connect net/socket.c:1923 [inline]
       __se_sys_connect net/socket.c:1920 [inline]
       __x64_sys_connect+0x6f/0xb0 net/socket.c:1920
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain kernel/locking/lockdep.c:3789 [inline]
       __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
       lock_acquire kernel/locking/lockdep.c:5625 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
       lock_sock_nested+0xca/0x120 net/core/sock.c:3191
       lock_sock include/net/sock.h:1612 [inline]
       rfcomm_sk_state_change+0xb4/0x390 net/bluetooth/rfcomm/sock.c:73
       __rfcomm_dlc_close+0x1b6/0x8a0 net/bluetooth/rfcomm/core.c:489
       rfcomm_process_dlcs net/bluetooth/rfcomm/core.c:1844 [inline]
       rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2003 [inline]
       rfcomm_run+0xf1e/0x4a20 net/bluetooth/rfcomm/core.c:2086
       kthread+0x3e5/0x4d0 kernel/kthread.c:319
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_mutex --> &d->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&d->lock);
                               lock(rfcomm_mutex);
                               lock(&d->lock);
  lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);

 *** DEADLOCK ***

2 locks held by krfcommd/2873:
 #0: ffffffff8d31d728 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_process_sessions net/bluetooth/rfcomm/core.c:1979 [inline]
 #0: ffffffff8d31d728 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_run+0x2ed/0x4a20 net/bluetooth/rfcomm/core.c:2086
 #1: ffff88807cfe0928 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x162/0x8a0 net/bluetooth/rfcomm/core.c:487

stack backtrace:
CPU: 1 PID: 2873 Comm: krfcommd Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131
 check_prev_add kernel/locking/lockdep.c:3051 [inline]
 check_prevs_add kernel/locking/lockdep.c:3174 [inline]
 validate_chain kernel/locking/lockdep.c:3789 [inline]
 __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
 lock_acquire kernel/locking/lockdep.c:5625 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
 lock_sock_nested+0xca/0x120 net/core/sock.c:3191
 lock_sock include/net/sock.h:1612 [inline]
 rfcomm_sk_state_change+0xb4/0x390 net/bluetooth/rfcomm/sock.c:73
 __rfcomm_dlc_close+0x1b6/0x8a0 net/bluetooth/rfcomm/core.c:489
 rfcomm_process_dlcs net/bluetooth/rfcomm/core.c:1844 [inline]
 rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2003 [inline]
 rfcomm_run+0xf1e/0x4a20 net/bluetooth/rfcomm/core.c:2086
 kthread+0x3e5/0x4d0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295