------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 13771 at lib/refcount.c:25 refcount_warn_saturate+0x80/0xe0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 13771 Comm: kworker/u5:0 Not tainted 5.11.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: hci0 hci_rx_work RIP: 0010:refcount_warn_saturate+0x80/0xe0 lib/refcount.c:25 Code: 05 ba 76 bf 02 01 e8 43 62 34 01 0f 0b c3 80 3d aa 76 bf 02 00 75 b8 48 c7 c7 f0 e4 f7 83 c6 05 9a 76 bf 02 01 e8 24 62 34 01 <0f> 0b c3 80 3d 8d 76 bf 02 00 75 99 48 c7 c7 c8 e4 f7 83 c6 05 7d RSP: 0018:ffffc90000d33cc8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002 RDX: 0000000080000002 RSI: ffffffff84087901 RDI: 00000000ffffffff RBP: ffff8881136fe000 R08: 0000000000000001 R09: 0000000000000001 R10: ffffc90000d33af8 R11: ffffc90000d33af0 R12: 0000000000000000 R13: 0000000000000001 R14: ffffffff84851148 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fff3413cb04 CR3: 00000001043e7000 CR4: 0000000000350ef0 Call Trace: __refcount_add include/linux/refcount.h:199 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] l2cap_chan_hold net/bluetooth/l2cap_core.c:495 [inline] l2cap_global_chan_by_psm+0x1f8/0x220 net/bluetooth/l2cap_core.c:1984 l2cap_conless_channel net/bluetooth/l2cap_core.c:7602 [inline] l2cap_recv_frame+0x554/0x2e40 net/bluetooth/l2cap_core.c:7672 hci_acldata_packet net/bluetooth/hci_core.c:4785 [inline] hci_rx_work+0x1d3/0x500 net/bluetooth/hci_core.c:4976 process_one_work+0x293/0x600 kernel/workqueue.c:2275 worker_thread+0x38/0x380 kernel/workqueue.c:2421 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296