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Date: Wed, 17 Apr 2024 08:30:00 +0200
From: Johan Hovold <johan@kernel.org>
To: Zijun Hu <quic_zijuhu@quicinc.com>
Cc: luiz.dentz@gmail.com, marcel@holtmann.org,
	linux-bluetooth@vger.kernel.org, johan+linaro@kernel.org
Subject: Re: [PATCH] Bluetooth: qca: Fix nullptr dereference for non-serdev
 devices
Message-ID: <Zh9saGbOl-fXP6SD@hovoldconsulting.com>
References: <1713325792-17181-1-git-send-email-quic_zijuhu@quicinc.com>
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In-Reply-To: <1713325792-17181-1-git-send-email-quic_zijuhu@quicinc.com>

On Wed, Apr 17, 2024 at 11:49:52AM +0800, Zijun Hu wrote:
> hu->serdev is nullptr and will cause nullptr dereference if qca_setup()
> is called by non-serdev device, fixed by null check before access.

No, this patch is not correct.
 
> Fixes: 77f45cca8bc5 ("Bluetooth: qca: fix device-address endianness")
> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
> ---
>  drivers/bluetooth/hci_qca.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 92fa20f5ac7d..9c6573c727e1 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -1905,10 +1905,11 @@ static int qca_setup(struct hci_uart *hu)
>  	case QCA_WCN6750:
>  	case QCA_WCN6855:
>  	case QCA_WCN7850:
> -		qcadev = serdev_device_get_drvdata(hu->serdev);

Non-serdev controllers have type QCA_ROME (see qca_soc_type()) so will
never end up in this path.

I verified this when I wrote the patch and also fixed up a couple of
real non-serdev bugs here:

	https://lore.kernel.org/lkml/20240319154611.2492-1-johan+linaro@kernel.org/

> -		if (qcadev->bdaddr_property_broken)
> -			set_bit(HCI_QUIRK_BDADDR_PROPERTY_BROKEN, &hdev->quirks);
> -
> +		if (hu->serdev) {
> +			qcadev = serdev_device_get_drvdata(hu->serdev);
> +			if (qcadev->bdaddr_property_broken)
> +				set_bit(HCI_QUIRK_BDADDR_PROPERTY_BROKEN, &hdev->quirks);
> +		}
>  		hci_set_aosp_capable(hdev);
>  
>  		ret = qca_read_soc_version(hdev, &ver, soc_type);

Johan