syzbot

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc2-syzkaller-00100-geb952c47d154 #0 Not tainted
------------------------------------------------------
syz.5.2609/15421 is trying to acquire lock:
ffffffff8fe5fdc8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_exists+0xa6/0x380 net/bluetooth/rfcomm/core.c:546

but task is already holding lock:
ffffffff8fe63928 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
ffffffff8fe63928 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x237/0x2220 net/bluetooth/rfcomm/tty.c:584

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (rfcomm_ioctl_mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
       rfcomm_dev_ioctl+0x237/0x2220 net/bluetooth/rfcomm/tty.c:584
       rfcomm_sock_ioctl+0x86/0xd0 net/bluetooth/rfcomm/sock.c:869
       sock_do_ioctl+0x15a/0x460 net/socket.c:1227
       sock_ioctl+0x626/0x8e0 net/socket.c:1346
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       lock_sock_nested+0x48/0x100 net/core/sock.c:3611
       lock_sock include/net/sock.h:1609 [inline]
       rfcomm_sk_state_change+0x5b/0x310 net/bluetooth/rfcomm/sock.c:73
       __rfcomm_dlc_close+0x271/0x6a0 net/bluetooth/rfcomm/core.c:493
       rfcomm_dlc_close+0xf1/0x190 net/bluetooth/rfcomm/core.c:524
       __rfcomm_sock_close+0x121/0x250 net/bluetooth/rfcomm/sock.c:220
       rfcomm_sock_shutdown+0xb8/0x240 net/bluetooth/rfcomm/sock.c:901
       rfcomm_sock_release+0x59/0x120 net/bluetooth/rfcomm/sock.c:922
       __sock_release net/socket.c:658 [inline]
       sock_close+0xbe/0x240 net/socket.c:1426
       __fput+0x241/0x880 fs/file_table.c:431
       task_work_run+0x251/0x310 kernel/task_work.c:228
       get_signal+0x15e8/0x1740 kernel/signal.c:2690
       arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
       exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
       exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
       __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
       syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
       do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&d->lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       __rfcomm_dlc_close+0x226/0x6a0 net/bluetooth/rfcomm/core.c:491
       rfcomm_dlc_close+0xf1/0x190 net/bluetooth/rfcomm/core.c:524
       __rfcomm_sock_close+0x121/0x250 net/bluetooth/rfcomm/sock.c:220
       rfcomm_sock_shutdown+0xb8/0x240 net/bluetooth/rfcomm/sock.c:901
       rfcomm_sock_release+0x59/0x120 net/bluetooth/rfcomm/sock.c:922
       __sock_release net/socket.c:658 [inline]
       sock_close+0xbe/0x240 net/socket.c:1426
       __fput+0x241/0x880 fs/file_table.c:431
       task_work_run+0x251/0x310 kernel/task_work.c:228
       get_signal+0x15e8/0x1740 kernel/signal.c:2690
       arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
       exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
       exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
       __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
       syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
       do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rfcomm_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       rfcomm_dlc_exists+0xa6/0x380 net/bluetooth/rfcomm/core.c:546
       __rfcomm_create_dev net/bluetooth/rfcomm/tty.c:414 [inline]
       rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
       rfcomm_dev_ioctl+0xb53/0x2220 net/bluetooth/rfcomm/tty.c:584
       rfcomm_sock_ioctl+0x86/0xd0 net/bluetooth/rfcomm/sock.c:869
       sock_do_ioctl+0x15a/0x460 net/socket.c:1227
       sock_ioctl+0x626/0x8e0 net/socket.c:1346
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  rfcomm_mutex --> sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_ioctl_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rfcomm_ioctl_mutex);
                               lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);
                               lock(rfcomm_ioctl_mutex);
  lock(rfcomm_mutex);

 *** DEADLOCK ***

2 locks held by syz.5.2609/15421:
 #0: ffff8880245db258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
 #0: ffff8880245db258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_ioctl+0x78/0xd0 net/bluetooth/rfcomm/sock.c:868
 #1: ffffffff8fe63928 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
 #1: ffffffff8fe63928 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x237/0x2220 net/bluetooth/rfcomm/tty.c:584

stack backtrace:
CPU: 0 UID: 0 PID: 15421 Comm: syz.5.2609 Not tainted 6.12.0-rc2-syzkaller-00100-geb952c47d154 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 rfcomm_dlc_exists+0xa6/0x380 net/bluetooth/rfcomm/core.c:546
 __rfcomm_create_dev net/bluetooth/rfcomm/tty.c:414 [inline]
 rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
 rfcomm_dev_ioctl+0xb53/0x2220 net/bluetooth/rfcomm/tty.c:584
 rfcomm_sock_ioctl+0x86/0xd0 net/bluetooth/rfcomm/sock.c:869
 sock_do_ioctl+0x15a/0x460 net/socket.c:1227
 sock_ioctl+0x626/0x8e0 net/socket.c:1346
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feed8b7dff9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feed98b7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007feed8d36058 RCX: 00007feed8b7dff9
RDX: 0000000020000100 RSI: 00000000400452c8 RDI: 0000000000000009
RBP: 00007feed8bf0296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007feed8d36058 R15: 00007ffe677563e8
 </TASK>