======================================================
WARNING: possible circular locking dependency detected
5.15.0-rc4-next-20211008-syzkaller #0 Not tainted
------------------------------------------------------
krfcommd/2714 is trying to acquire lock:
ffff88807acaf120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1637 [inline]
ffff88807acaf120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73

but task is already holding lock:
ffff8880737bdd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x281/0x480 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}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5637
       __mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:599
       __mutex_lock kernel/locking/mutex.c:732 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:784
       __rfcomm_dlc_close+0x281/0x480 net/bluetooth/rfcomm/core.c:487
       rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1880
       rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2039
       rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2122
       kthread+0x468/0x490 kernel/kthread.c:327
       ret_from_fork+0x1f/0x30

-> #1 (rfcomm_mutex){+.+.}-{3:3}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5637
       __mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:599
       __mutex_lock kernel/locking/mutex.c:732 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:784
       rfcomm_dlc_open+0x25/0x50 net/bluetooth/rfcomm/core.c:425
       rfcomm_sock_connect+0x285/0x470 net/bluetooth/rfcomm/sock.c:413
       __sys_connect_file net/socket.c:1896 [inline]
       __sys_connect+0x29b/0x2d0 net/socket.c:1913
       __do_sys_connect net/socket.c:1923 [inline]
       __se_sys_connect net/socket.c:1920 [inline]
       __x64_sys_connect+0x76/0x80 net/socket.c:1920
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x44/0xd0 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:3063 [inline]
       check_prevs_add kernel/locking/lockdep.c:3186 [inline]
       validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3801
       __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5027
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5637
       lock_sock_nested+0x4a/0x100 net/core/sock.c:3272
       lock_sock include/net/sock.h:1637 [inline]
       rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73
       __rfcomm_dlc_close+0x2cc/0x480 net/bluetooth/rfcomm/core.c:489
       rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1880
       rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2039
       rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2122
       kthread+0x468/0x490 kernel/kthread.c:327
       ret_from_fork+0x1f/0x30

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/2714:
 #0: ffffffff8ded4ea8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_process_sessions+0x21/0x3f0 net/bluetooth/rfcomm/core.c:2015
 #1: ffff8880737bdd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x281/0x480 net/bluetooth/rfcomm/core.c:487

stack backtrace:
CPU: 0 PID: 2714 Comm: krfcommd Not tainted 5.15.0-rc4-next-20211008-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
 check_noncircular+0x2f9/0x3b0 kernel/locking/lockdep.c:2143
 check_prev_add kernel/locking/lockdep.c:3063 [inline]
 check_prevs_add kernel/locking/lockdep.c:3186 [inline]
 validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3801
 __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5027
 lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5637
 lock_sock_nested+0x4a/0x100 net/core/sock.c:3272
 lock_sock include/net/sock.h:1637 [inline]
 rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73
 __rfcomm_dlc_close+0x2cc/0x480 net/bluetooth/rfcomm/core.c:489
 rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1880
 rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2039
 rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2122
 kthread+0x468/0x490 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30
 </TASK>