------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28, CPU#0: syz-executor/26490 Modules linked in: CPU: 0 UID: 0 PID: 26490 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28 Code: 04 8b fe 0a 67 48 0f b9 3a eb 4a e8 a8 fd 32 fd 48 8d 3d 01 8b fe 0a 67 48 0f b9 3a eb 37 e8 95 fd 32 fd 48 8d 3d fe 8a fe 0a <67> 48 0f b9 3a eb 24 e8 82 fd 32 fd 48 8d 3d fb 8a fe 0a 67 48 0f RSP: 0018:ffffc900038f77f8 EFLAGS: 00010293 RAX: ffffffff848dfa2b RBX: 0000000000000003 RCX: ffff8880240ddb80 RDX: 0000000000000000 RSI: ffffffff8e68e140 RDI: ffffffff8f8c8530 RBP: 0000000000000000 R08: ffff8880240ddb80 R09: 0000000000000005 R10: 0000000000000004 R11: 0000000000000000 R12: ffff88801e750c00 R13: ffff88805fd26460 R14: ffff88805fd26478 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff888125e1f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555558603588 CR3: 0000000083194000 CR4: 00000000003526f0 Call Trace: __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+0x3c7/0x3d0 lib/klist.c:206 klist_put lib/klist.c:217 [inline] klist_del lib/klist.c:230 [inline] klist_remove+0x1bd/0x340 lib/klist.c:249 device_move+0x193/0x730 drivers/base/core.c:4615 hci_conn_del_sysfs+0xb8/0x1a0 net/bluetooth/hci_sysfs.c:75 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline] hci_conn_del+0xc36/0x1240 net/bluetooth/hci_conn.c:1234 hci_conn_hash_flush+0x191/0x260 net/bluetooth/hci_conn.c:2638 hci_dev_close_sync+0x821/0x1100 net/bluetooth/hci_sync.c:5327 hci_dev_do_close net/bluetooth/hci_core.c:501 [inline] hci_unregister_dev+0x21a/0x5b0 net/bluetooth/hci_core.c:2715 vhci_release+0x152/0x1a0 drivers/bluetooth/hci_vhci.c:690 __fput+0x44c/0xa70 fs/file_table.c:468 task_work_run+0x1d4/0x260 kernel/task_work.c:233 exit_task_work include/linux/task_work.h:40 [inline] do_exit+0x694/0x22f0 kernel/exit.c:971 do_group_exit+0x21c/0x2d0 kernel/exit.c:1112 __do_sys_exit_group kernel/exit.c:1123 [inline] __se_sys_exit_group kernel/exit.c:1121 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121 x64_sys_call+0x2210/0x2210 arch/x86/include/generated/asm/syscalls_64.h:232 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f39ec58f749 Code: Unable to access opcode bytes at 0x7f39ec58f71f. RSP: 002b:00007fff5852c9b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 00007f39ec58f749 RDX: 00007f39ec59163a RSI: 0000000000000000 RDI: 0000000000000007 RBP: 0000000000000003 R08: 0079746972756365 R09: 0000000000000007 R10: 00000000000003b8 R11: 0000000000000246 R12: 00007f39ec7b5ca0 R13: 00007fff5852d56c R14: 0000000000000000 R15: 00007f39ec7b7e60 ---------------- Code disassembly (best guess): 0: 04 8b add $0x8b,%al 2: fe 0a decb (%rdx) 4: 67 48 0f b9 3a ud1 (%edx),%rdi 9: eb 4a jmp 0x55 b: e8 a8 fd 32 fd call 0xfd32fdb8 10: 48 8d 3d 01 8b fe 0a lea 0xafe8b01(%rip),%rdi # 0xafe8b18 17: 67 48 0f b9 3a ud1 (%edx),%rdi 1c: eb 37 jmp 0x55 1e: e8 95 fd 32 fd call 0xfd32fdb8 23: 48 8d 3d fe 8a fe 0a lea 0xafe8afe(%rip),%rdi # 0xafe8b28 * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: eb 24 jmp 0x55 31: e8 82 fd 32 fd call 0xfd32fdb8 36: 48 8d 3d fb 8a fe 0a lea 0xafe8afb(%rip),%rdi # 0xafe8b38 3d: 67 addr32 3e: 48 rex.W 3f: 0f .byte 0xf