======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.0/5320 is trying to acquire lock:
ffffffff903fe5e0 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_close+0x3a/0x1b0 net/bluetooth/rfcomm/core.c:508

but task is already holding lock:
ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline]
ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline]
ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe8/0x340 net/bluetooth/rfcomm/sock.c:224

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+0x41/0x100 net/core/sock.c:3830
       lock_sock include/net/sock.h:1713 [inline]
       rfcomm_connect_ind+0x4e3/0xa30 net/bluetooth/rfcomm/sock.c:968
       rfcomm_recv_pn net/bluetooth/rfcomm/core.c:1509 [inline]
       rfcomm_recv_mcc net/bluetooth/rfcomm/core.c:1727 [inline]
       rfcomm_recv_frame net/bluetooth/rfcomm/core.c:1868 [inline]
       rfcomm_process_rx+0x35fb/0x6cf0 net/bluetooth/rfcomm/core.c:2020
       rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2114 [inline]
       rfcomm_run+0xae8/0x2ce0 net/bluetooth/rfcomm/core.c:2204
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (rfcomm_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       rfcomm_dlc_close+0x3a/0x1b0 net/bluetooth/rfcomm/core.c:508
       __rfcomm_sock_close+0x1a4/0x340 net/bluetooth/rfcomm/sock.c:231
       rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline]
       rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline]
       __rfcomm_sock_close+0xf0/0x340 net/bluetooth/rfcomm/sock.c:224
       rfcomm_sock_shutdown+0xc2/0x270 net/bluetooth/rfcomm/sock.c:920
       rfcomm_sock_release+0x59/0x170 net/bluetooth/rfcomm/sock.c:941
       __sock_release+0xa0/0x1f0 net/socket.c:735
       sock_close+0x1c/0x30 net/socket.c:1526
       __fput+0x418/0xa50 fs/file_table.c:512
       task_work_run+0x1d9/0x270 kernel/task_work.c:233
       resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
       __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
       exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
       __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
       syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
       syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
       do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

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 ***

locks held by syz.0.0/5320: 2, last CPU#0:
 #0: ffff88804427d940 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #0: ffff88804427d940 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x7a/0x1f0 net/socket.c:734
 #1: ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #1: ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_close net/bluetooth/rfcomm/sock.c:245 [inline]
 #1: ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline]
 #1: ffff8880506ba260 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: __rfcomm_sock_close+0xe8/0x340 net/bluetooth/rfcomm/sock.c:224

stack backtrace:
CPU: 0 UID: 0 PID: 5320 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 rfcomm_dlc_close+0x3a/0x1b0 net/bluetooth/rfcomm/core.c:508
 __rfcomm_sock_close+0x1a4/0x340 net/bluetooth/rfcomm/sock.c:231
 rfcomm_sock_close net/bluetooth/rfcomm/sock.c:246 [inline]
 rfcomm_sock_cleanup_listen net/bluetooth/rfcomm/sock.c:190 [inline]
 __rfcomm_sock_close+0xf0/0x340 net/bluetooth/rfcomm/sock.c:224
 rfcomm_sock_shutdown+0xc2/0x270 net/bluetooth/rfcomm/sock.c:920
 rfcomm_sock_release+0x59/0x170 net/bluetooth/rfcomm/sock.c:941
 __sock_release+0xa0/0x1f0 net/socket.c:735
 sock_close+0x1c/0x30 net/socket.c:1526
 __fput+0x418/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5bf6d9e159
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:00007fff15511958 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff15511a40 RCX: 00007f5bf6d9e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000170fc R08: 0000000000000001 R09: 0000000000000000
R10: 00007f5bf6bff02c R11: 0000000000000246 R12: 00007fff15511a80
R13: 00007f5bf7025fac R14: 0000000000017142 R15: 00007f5bf7025fa0
 </TASK>