syzbot

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refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 3805 at lib/refcount.c:25 refcount_warn_saturate+0x13d/0x1a0 lib/refcount.c:25
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 3805 Comm: krfcommd Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 panic+0x264/0x7a0 kernel/panic.c:231
 __warn+0x227/0x250 kernel/panic.c:600
 report_bug+0x1b1/0x2e0 lib/bug.c:198
 handle_bug+0x42/0x80 arch/x86/kernel/traps.c:235
 exc_invalid_op+0x16/0x40 arch/x86/kernel/traps.c:255
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
RIP: 0010:refcount_warn_saturate+0x13d/0x1a0 lib/refcount.c:25
Code: c7 93 1e 15 89 31 c0 e8 71 0c a9 fd 0f 0b eb a3 e8 88 66 d7 fd c6 05 97 4d ed 05 01 48 c7 c7 ca 1e 15 89 31 c0 e8 53 0c a9 fd <0f> 0b eb 85 e8 6a 66 d7 fd c6 05 7a 4d ed 05 01 48 c7 c7 f6 1e 15
RSP: 0018:ffffc90001997b80 EFLAGS: 00010246
RAX: b5077223a4630100 RBX: 0000000000000002 RCX: ffff88809902e380
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffffff815dffd9 R09: ffffed1015d262c0
R10: ffffed1015d262c0 R11: 0000000000000000 R12: ffff88808df4b4b8
R13: ffff88808df4b080 R14: 0000000000000000 R15: dffffc0000000000
 refcount_add include/linux/refcount.h:205 [inline]
 refcount_inc include/linux/refcount.h:241 [inline]
 sock_hold include/net/sock.h:692 [inline]
 bt_accept_dequeue+0x34e/0x560 net/bluetooth/af_bluetooth.c:206
 l2cap_sock_accept+0x21c/0x430 net/bluetooth/l2cap_sock.c:332
 kernel_accept+0x143/0x410 net/socket.c:3569
 rfcomm_accept_connection net/bluetooth/rfcomm/core.c:1931 [inline]
 rfcomm_process_sessions+0x1c5/0xc540 net/bluetooth/rfcomm/core.c:1990
 rfcomm_run+0x3b5/0x900 net/bluetooth/rfcomm/core.c:2086
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Kernel Offset: disabled
Rebooting in 86400 seconds..