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

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Message-Id: <73AF4476-F5B2-4E83-9F43-72D98B4615FF@holtmann.org>
Date:   Mon, 15 Nov 2021 18:27:33 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Jackie Liu <liu.yun@...ux.dev>
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 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;
		}
	}

Regards

Marcel