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Subject: Re: [PATCH v1] bluetooth: guard against controllers sending zero'd
 events
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20200228205146.161229-1-alainm@chromium.org>
Date:   Sat, 29 Feb 2020 08:14:54 +0100
Cc:     linux-bluetooth@vger.kernel.org
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Message-Id: <788439D3-E0CC-4CBA-99C2-0B9C3703B23D@holtmann.org>
References: <20200228205146.161229-1-alainm@chromium.org>
To:     Alain Michaud <alainm@chromium.org>
Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

Hi Alain,

> Some controllers have been observed to send zero'd events under some
> conditions.  This change guards against this condition as well as adding
> a trace to facilitate diagnosability of this condition.

can you include a trace for this as well please.

> 
> Signed-off-by: Alain Michaud <alainm@chromium.org>
> ---
> 
> net/bluetooth/hci_event.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 591e7477e925..f865eddb8d69 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -5868,7 +5868,8 @@ void hci_event_packet(struct hci_dev *hdev, struct sk_buff *skb)
> 	u8 status = 0, event = hdr->evt, req_evt = 0;
> 	u16 opcode = HCI_OP_NOP;
> 
> -	if (hdev->sent_cmd && bt_cb(hdev->sent_cmd)->hci.req_event == event) {
> +	if (hdev->sent_cmd && event &&
> +	    bt_cb(hdev->sent_cmd)->hci.req_event == event) {

Why are you bothering to check for event here. Do we have requests set with hci_req.event == 0?

> 		struct hci_command_hdr *cmd_hdr = (void *) hdev->sent_cmd->data;
> 		opcode = __le16_to_cpu(cmd_hdr->opcode);
> 		hci_req_cmd_complete(hdev, opcode, status, &req_complete,
> @@ -5876,6 +5877,9 @@ void hci_event_packet(struct hci_dev *hdev, struct sk_buff *skb)
> 		req_evt = event;
> 	}
> 
> +	if (!event)
> +		BT_ERR("Received unexpected HCI Event 00000000");
> +

We need to start using bt_dev_err if we want to do that. However in this case bt_dev_warn is better since we should be gracefully handling this anyway.

Regards

Marcel