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

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Message-ID: <bc2cd818-c7ad-9061-29ce-f5390d44d8ab@huawei.com>
Date:   Wed, 26 Jul 2023 14:44:01 +0800
From:   liulongfang <liulongfang@...wei.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] USB:bugfix a controller halt error

On 2023/7/21 19:08, Greg KH Wrote:
> 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?
>

This is a test conducted under a special test scenario.
ECC memory errors are caused by some test tools.

>> 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

You are right. I made a patch error here. The code modification should be like this:
if (r < 0) {
	retval = r;
	kfree(buf);
	goto fail;
}

thanks,

Longfang.
> I missing?
> 
> thanks,
> 
> greg k-h
> .
>