linux-kernel - Re: [PATCH] USB:bugfix a controller halt error

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Message-ID: <2023072153-module-wannabe-5637@gregkh>
Date:   Fri, 21 Jul 2023 13:08:18 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     liulongfang <liulongfang@...wei.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB:bugfix a controller halt error

On Fri, Jul 21, 2023 at 06:00:15PM +0800, liulongfang wrote:
> On systems that use ECC memory. The ECC error of the memory will
> cause the USB controller to halt. It causes the usb_control_msg()
> operation to fail.

Why does ECC memory matter here?

> At this point, the returned buffer data is an abnormal value, and
> continuing to use it will lead to incorrect results.
> 
> Therefore, it is necessary to judge the return value and exit.
> 
> Signed-off-by: liulongfang <liulongfang@...wei.com>
> ---
>  drivers/usb/core/hub.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index a739403a9e45..6a43198be263 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -4891,6 +4891,16 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
>  					USB_DT_DEVICE << 8, 0,
>  					buf, GET_DESCRIPTOR_BUFSIZE,
>  					initial_descriptor_timeout);
> +				/* On systems that use ECC memory, ECC errors can
> +				 * cause the USB controller to halt.
> +				 * It causes this operation to fail. At this time,
> +				 * the buf data is an abnormal value and needs to be exited.
> +				 */
> +				if (r < 0) {
> +					kfree(buf);
> +					goto fail;
> +				}

Are you sure this is correct?  How was this tested?  Seems to me that
this will still return "success" if this code path ever happens, what am
I missing?

thanks,

greg k-h