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Date: Thu, 16 May 2024 22:55:26 +0800
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Subject: Re: [PATCH v2] Bluetooth: qca: Fix BT enable failure again for
 QCA6390 after warm reboot
To: Zijun Hu <quic_zijuhu@quicinc.com>, luiz.dentz@gmail.com,
 luiz.von.dentz@intel.com, marcel@holtmann.org
Cc: linux-bluetooth@vger.kernel.org, wt@penguintechs.org,
 regressions@lists.linux.dev, pmenzel@molgen.mpg.de,
 krzysztof.kozlowski@linaro.org, stable@vger.kernel.org
References: <1715866294-1549-1-git-send-email-quic_zijuhu@quicinc.com>
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From: Lk Sii <lk_sii@163.com>
In-Reply-To: <1715866294-1549-1-git-send-email-quic_zijuhu@quicinc.com>
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On 2024/5/16 21:31, Zijun Hu wrote:
> Commit 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on closed
> serdev") will cause below regression issue:
> 
> BT can't be enabled after below steps:
> cold boot -> enable BT -> disable BT -> warm reboot -> BT enable failure
> if property enable-gpios is not configured within DT|ACPI for QCA6390.
> 
> The commit is to fix a use-after-free issue within qca_serdev_shutdown()
> by adding condition to avoid the serdev is flushed or wrote after closed
> but also introduces this regression issue regarding above steps since the
> VSC is not sent to reset controller during warm reboot.
> 
> Fixed by sending the VSC to reset controller within qca_serdev_shutdown()
> once BT was ever enabled, and the use-after-free issue is also fixed by
> this change since the serdev is still opened before it is flushed or wrote.
> 
> Verified by the reported machine Dell XPS 13 9310 laptop over below two
> kernel commits:
> commit e00fc2700a3f ("Bluetooth: btusb: Fix triggering coredump
> implementation for QCA") of bluetooth-next tree.
> commit b23d98d46d28 ("Bluetooth: btusb: Fix triggering coredump
> implementation for QCA") of linus mainline tree.
> 
> Fixes: 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on closed serdev")
> Cc: stable@vger.kernel.org
> Reported-by: Wren Turkal <wt@penguintechs.org>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218726
> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
> Tested-by: Wren Turkal <wt@penguintechs.org>
> ---
> V1 -> V2: Add comments and more commit messages
> 
> V1 discussion link:
> https://lore.kernel.org/linux-bluetooth/d553edef-c1a4-4d52-a892-715549d31ebe@163.com/T/#t
> 
>  drivers/bluetooth/hci_qca.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 0c9c9ee56592..9a0bc86f9aac 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -2450,15 +2450,27 @@ static void qca_serdev_shutdown(struct device *dev)
>  	struct qca_serdev *qcadev = serdev_device_get_drvdata(serdev);
>  	struct hci_uart *hu = &qcadev->serdev_hu;
>  	struct hci_dev *hdev = hu->hdev;
> -	struct qca_data *qca = hu->priv;
>  	const u8 ibs_wake_cmd[] = { 0xFD };
>  	const u8 edl_reset_soc_cmd[] = { 0x01, 0x00, 0xFC, 0x01, 0x05 };
>  
>  	if (qcadev->btsoc_type == QCA_QCA6390) {
> -		if (test_bit(QCA_BT_OFF, &qca->flags) ||
> -		    !test_bit(HCI_RUNNING, &hdev->flags))
> +		/* The purpose of sending the VSC is to reset SOC into a initial
> +		 * state and the state will ensure next hdev->setup() success.
> +		 * if HCI_QUIRK_NON_PERSISTENT_SETUP is set, it means that
> +		 * hdev->setup() can do its job regardless of SoC state, so
> +		 * don't need to send the VSC.
> +		 * if HCI_SETUP is set, it means that hdev->setup() was never
> +		 * invoked and the SOC is already in the initial state, so
> +		 * don't also need to send the VSC.
> +		 */
> +		if (test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks) ||
> +		    hci_dev_test_flag(hdev, HCI_SETUP))
>  			return;
>  
> +		/* The serdev must be in open state when conrol logic arrives
> +		 * here, so also fix the use-after-free issue caused by that
> +		 * the serdev is flushed or wrote after it is closed.
> +		 */
>  		serdev_device_write_flush(serdev);
>  		ret = serdev_device_write_buf(serdev, ibs_wake_cmd,
>  					      sizeof(ibs_wake_cmd));
i believe Zijun's change is able to fix both below issues and don't
introduce new issue.

regression issue A:  BT enable failure after warm reboot.
issue B:  use-after-free issue, namely, kernel crash.


For issue B, i have more findings related to below commits ordered by time.

Commit A: 7e7bbddd029b ("Bluetooth: hci_qca: Fix qca6390 enable failure
after warm reboot")

Commit B: de8892df72be ("Bluetooth: hci_serdev: Close UART port if
NON_PERSISTENT_SETUP is set")
this commit introduces issue B, it is also not suitable to associate
protocol state with state of lower level transport type such as serdev
or uart, in my opinion, protocol state should be independent with
transport type state, flag HCI_UART_PROTO_READY is for protocol state,
it means if protocol hu->proto is initialized and if we can invoke its
interfaces.it is common for various kinds of transport types. perhaps,
this is the reason why Zijun's change doesn't use flag HCI_UART_PROTO_READY.

Commit C: 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on
closed serdev")
this commit is to fix issue B which is actually caused by Commit B, but
it has Fixes tag for Commit A. and it also introduces the regression
issue A.