netdev - Re: [PATCH] bluetooth: fix uninitialized variables notify

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Date:   Tue, 16 Nov 2021 08:46:55 +0800
From:   Jackie Liu <liu.yun@...ux.dev>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     "Tumkur Narayan, Chethan" <chethan.tumkur.narayan@...el.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] bluetooth: fix uninitialized variables notify_evt

Hi, Marcel.

在 2021/11/16 上午1:27, Marcel Holtmann 写道:
> Hi Jackie,
> 
>> Coverity Scan report:
>>
>> [...]
>> *** CID 1493985:  Uninitialized variables  (UNINIT)
>> /net/bluetooth/hci_event.c: 4535 in hci_sync_conn_complete_evt()
>> 4529
>> 4530     	/* Notify only in case of SCO over HCI transport data path which
>> 4531     	 * is zero and non-zero value shall be non-HCI transport data path
>> 4532     	 */
>> 4533     	if (conn->codec.data_path == 0) {
>> 4534     		if (hdev->notify)
>>>>>     CID 1493985:  Uninitialized variables  (UNINIT)
>>>>>     Using uninitialized value "notify_evt" when calling "*hdev->notify".
>> 4535     			hdev->notify(hdev, notify_evt);
>> 4536     	}
>> 4537
>> 4538     	hci_connect_cfm(conn, ev->status);
>> 4539     	if (ev->status)
>> 4540     		hci_conn_del(conn);
>> [...]
>>
>> Although only btusb uses air_mode, and he only handles HCI_NOTIFY_ENABLE_SCO_CVSD
>> and HCI_NOTIFY_ENABLE_SCO_TRANSP, there is still a very small chance that
>> ev->air_mode is not equal to 0x2 and 0x3, but notify_evt is initialized to
>> HCI_NOTIFY_ENABLE_SCO_CVSD or HCI_NOTIFY_ENABLE_SCO_TRANSP. the context is
>> maybe not correct.
>>
>> In order to ensure 100% correctness, we directly give him a default value 0.
>>
>> Addresses-Coverity: ("Uninitialized variables")
>> Fixes: f4f9fa0c07bb ("Bluetooth: Allow usb to auto-suspend when SCO use	non-HCI transport")
>> Signed-off-by: Jackie Liu <liuyun01@...inos.cn>
>> ---
>> net/bluetooth/hci_event.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>> index 7d0db1ca1248..f898fa42a183 100644
>> --- a/net/bluetooth/hci_event.c
>> +++ b/net/bluetooth/hci_event.c
>> @@ -4445,7 +4445,7 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
>> {
>> 	struct hci_ev_sync_conn_complete *ev = (void *) skb->data;
>> 	struct hci_conn *conn;
>> -	unsigned int notify_evt;
>> +	unsigned int notify_evt = 0;
>>
>> 	BT_DBG("%s status 0x%2.2x", hdev->name, ev->status);
> 
> lets modify the switch statement and add a default case. And then lets add a check to notify_evt != 0.
> 
> With that in mind, I wonder if this is not better
> 
>          /* Notify only in case of SCO over HCI transport data path which
>           * is zero and non-zero value shall be non-HCI transport data path
>           */
> 	if (conn->codec.data_path == 0 && hdev->notify) {
> 		switch (ev->air_mode) {
> 		case 0x02:
> 			hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_CVSD);
> 			break;
> 		case 0x03:
> 			hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_TRANSP);
> 			break;
> 		}
> 	}

I prefer this, because it is a restoration of earlier logic, rather than
changing his logic. I will resend a patch, thank you.

--
Jackie Liu

> 
> Regards
> 
> Marcel
>