linux-kernel - RE: [PATCH] usb: xhci: lack of clearing xHC resources

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <PH7PR07MB95383C03E64507BED1D64222DDFB2@PH7PR07MB9538.namprd07.prod.outlook.com>
Date: Mon, 17 Feb 2025 06:25:35 +0000
From: Pawel Laszczak <pawell@...ence.com>
To: "stern@...land.harvard.edu" <stern@...land.harvard.edu>
CC: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        "christophe.jaillet@...adoo.fr" <christophe.jaillet@...adoo.fr>,
        "javier.carrasco@...fvision.net" <javier.carrasco@...fvision.net>,
        "make_ruc2021@....com" <make_ruc2021@....com>,
        "peter.chen@....com"
	<peter.chen@....com>,
        "linux-usb@...r.kernel.org"
	<linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        Pawel Eichler <peichler@...ence.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] usb: xhci: lack of clearing xHC resources

>
>
>On Thu, Feb 13, 2025 at 10:27:00AM +0000, Pawel Laszczak wrote:
>> The xHC resources allocated for USB devices are not released in correct
>order after resuming in case when while suspend device was reconnected.
>>
>> This issue has been detected during the fallowing scenario:
>> - connect hub HS to root port
>> - connect LS/FS device to hub port
>> - wait for enumeration to finish
>> - force DUT to suspend
>> - reconnect hub attached to root port
>> - wake DUT
>
>DUT refers to the host, not the LS/FS device plugged into the hub, is that
>right?

Yes DUT refers to the HOST.

>
>> For this scenario during enumeration of USB LS/FS device the Cadence xHC
>reports completion error code for xHCi commands because the devices was
>not property disconnected and in result the xHC resources has not been
>correct freed.
>> XHCI specification doesn't mention that device can be reset in any order so,
>we should not treat this issue as Cadence xHC controller bug.
>> Similar as during disconnecting in this case the device should be cleared
>starting form the last usb device in tree toward the root hub.
>> To fix this issue usbcore driver should disconnect all USB devices connected
>to hub which was reconnected while suspending.
>
>No, that's not right at all.  We do not want to disconnect these devices if
>there's any way to avoid it.
>
>There must be another way to tell the host controller to release the devices'
>resources.  Doesn't the usb_reset_and_verify_device() call do something like
>that anyway?  After all, the situation should be very similar to what happens
>when a device is simply reset.
>
>Alan Stern


Yes, I had such idea too, but the current solution is simpler.
I don't understand why in this case we can't do disconnect
The hub connected to host was physically disconnected during suspend, so 
It seems quite logic to make disconnection. 
Can you comment why we should not make disconnection?

Thanks,
Pawel