syzbot

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refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 9264 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 0 UID: 0 PID: 9264 Comm: syz.6.1276 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 28 ca e2 fc 84 db 0f 85 66 ff ff ff e8 3b cf e2 fc c6 05 10 1e 97 0b 01 90 48 c7 c7 e0 d9 f4 8b e8 27 fe a1 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 18 cf e2 fc 0f b6 1d eb 1d 97 0b 31
RSP: 0018:ffffc9000bb47738 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817aa908
RDX: ffff8880476f8000 RSI: ffffffff817aa915 RDI: 0000000000000001
RBP: ffff8880470ea078 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88802a111400
R13: ffff8880470ea078 R14: ffffffff86078b90 R15: ffffffff906a68a0
FS:  0000000000000000(0000) GS:ffff888124974000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f827cc00218 CR3: 00000000488d2000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 kref_put include/linux/kref.h:64 [inline]
 klist_dec_and_del lib/klist.c:206 [inline]
 klist_put+0x11b/0x1b0 lib/klist.c:217
 klist_del lib/klist.c:230 [inline]
 klist_remove+0x13f/0x2e0 lib/klist.c:249
 device_move+0x12d/0x10d0 drivers/base/core.c:4618
 hci_conn_del_sysfs+0x81/0x180 net/bluetooth/hci_sysfs.c:75
 hci_conn_cleanup net/bluetooth/hci_conn.c:175 [inline]
 hci_conn_del+0x566/0xdc0 net/bluetooth/hci_conn.c:1173
 hci_conn_hash_flush+0x186/0x260 net/bluetooth/hci_conn.c:2544
 hci_dev_close_sync+0x602/0x11d0 net/bluetooth/hci_sync.c:5225
 hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:483
 hci_unregister_dev+0x213/0x620 net/bluetooth/hci_core.c:2678
 vhci_release+0x79/0xf0 drivers/bluetooth/hci_vhci.c:665
 __fput+0x3ff/0xb70 fs/file_table.c:465
 task_work_run+0x150/0x240 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xae2/0x2c70 kernel/exit.c:959
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1108
 get_signal+0x2673/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x7d0 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5ea93c1225
Code: Unable to access opcode bytes at 0x7f5ea93c11fb.
RSP: 002b:00007f5ea71f5f80 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007f5ea95b5fa0 RCX: 00007f5ea93c1225
RDX: 00007f5ea71f5fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f5ea9410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f5ea95b5fa0 R15: 00007fff59843ff8
 </TASK>