Received-SPF: pass (google.com: domain of linux-bluetooth-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <b0cb4fb0-6b89-b9df-9ae6-421ac52b0100@pengutronix.de>
Date:   Thu, 16 Jun 2022 12:38:21 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.9.0
From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
Subject: Re: [BUG] BLE device unpairing triggers kernel panic
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        Marcel Holtmann <marcel@holtmann.org>,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>,
        Pengutronix Kernel Team <kernel@pengutronix.de>
References: <a1ce1743-e450-6cdb-dfab-56a3e3eb9aed@pengutronix.de>
 <CABBYNZ+z8kBUKGXbZSfb0ynJaTnPQRp0wFDUb12AW1ymbNx1eg@mail.gmail.com>
 <CABBYNZ+zsuggTpaUSPsZKeL=qqvM1=sgMWzdWEqaS_oh6dhY2g@mail.gmail.com>
 <8d5c4724-d511-39b1-21d7-116c91cada45@pengutronix.de>
Content-Language: en-US
In-Reply-To: <8d5c4724-d511-39b1-21d7-116c91cada45@pengutronix.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hello Luiz,

On 16.05.22 18:37, Ahmad Fatoum wrote:
>>>> - Commit a56a1138cbd8 ("Bluetooth: hci_sync: Fix not using conn_timeout")
>>>>   fixes, despite the title, what event is waited on. First Pairing works now,
>>>>   but the second pairing times out and crashes the kernel:
>>>>
>>>>   [   84.191684] Bluetooth: hci0: Opcode 0x200d failed: -110
>>>>   [   84.230478] Bluetooth: hci0: request failed to create LE connection: err -110
>>>>   [   84.237690] Unable to handle kernel read from unreadable memory at virtual address 0000000000000ca8
>>
>> That said the error -110 mean -ETIMEDOUT
> 
> Yes, this issue remains still. I feel better about my revert
> knowing that the crash is fixed, but I'd like this regression
> here fixed upstream as well. I'll try to collect some more
> information and report back.

I've now found time to revisit this and sprinkle around some
extra logging. This is the initial pairing that works:

  Bluetooth: entered hci_le_create_conn_sync()
  Bluetooth: hci0: opcode 0x200d plen 25
  Bluetooth: hci0: event 0x0f (sent = 0x0a)
  Bluetooth: hci0: BT: opcode 0x200d (sent: 0x0a)
  Bluetooth: hci0: event 0x3e (sent = 0x0a)
  Bluetooth: hci0: BT: subevent 0x0a (sent 0x0a)
  Bluetooth: entered hci_le_meta_evt(event=0x0a) completion clause

I unpaired on device side and then retried pairing:

  Bluetooth: entered hci_le_create_conn_sync()
  Bluetooth: hci0: opcode 0x200d plen 25
  Bluetooth: hci0: event 0x0f (sent = 0x0a)
  Bluetooth: hci0: BT: opcode 0x200d (sent: 0x0a)
  Bluetooth: entered hci_abort_conn()
  Bluetooth: hci0: opcode hci_req_add_ev 0x200e
  Bluetooth: hci0: event 0x0e (sent = 0x00)
  Bluetooth: hci0: event 0x3e (sent = 0x00)
  Bluetooth: hci0: BT: subevent 0x0a (sent 0x00)
  Bluetooth: __hci_cmd_sync_sk pending (event = 0x0a status=1, err=-110)
  Bluetooth: hci0: Opcode 0x200d failed: -110
  Bluetooth: hci0: opcode 0x2006 plen 15
  Bluetooth: hci0: event 0x0e (sent = 0x00)
  Bluetooth: hci0: opcode 0x200a plen 1
  Bluetooth: hci0: event 0x0e (sent = 0x00)
  Bluetooth: hci0: request failed to create LE connection: err -110


But now it times out as reported. It looks like the
intermittent hci_abort_conn() is at fault here. My theory is
that replacing hci->sent_cmd is the problem here, as other
events can't be matched anymore.

We've been deploying the revert for a while now and I just posted
it to the mailing list[1]. There have been other reports
of this issue with different hardware too and fixing sent_cmd
would likely be too complicated/time intensive for me.

I am happy to test future patches that fix this properly though.

[1]: https://lore.kernel.org/linux-bluetooth/20220616092418.738877-1-a.fatoum@pengutronix.de/T/#t

Cheers,
Ahmad


> 
> Cheers,
> Ahmad
> 


-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |