linux-kernel - Re: [REGRESSION 6.17-rc3] usb/xhci: possible memory leak after suspend/resume cycle.

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Message-ID: <7e8a138e.af64.19904ff3496.Coremail.00107082@163.com>
Date: Mon, 1 Sep 2025 19:17:38 +0800 (CST)
From: "David Wang" <00107082@....com>
To: "Mathias Nyman" <mathias.nyman@...ux.intel.com>
Cc: Michał Pecio <michal.pecio@...il.com>,
	WeitaoWang-oc@...oxin.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, regressions@...ts.linux.dev,
	linux-kernel@...r.kernel.org, surenb@...gle.com,
	kent.overstreet@...ux.dev
Subject: Re: [REGRESSION 6.17-rc3] usb/xhci: possible memory leak after
 suspend/resume cycle.


At 2025-09-01 18:14:32, "Mathias Nyman" <mathias.nyman@...ux.intel.com> wrote:
>On 30.8.2025 13.17, David Wang wrote:
>> 
>> At 2025-08-30 17:48:28, "Michał Pecio" <michal.pecio@...il.com> wrote:
>>>
>>> Hi,
>>>
>>> Good work, looks like suspend/resume is a little understested corner
>>> of this driver.
>>>
>>> Did you check whether the same leak occurs if you simply disconnect
>>> a device or if it's truly unique to suspend?
>>>
>>>> And bisect narrow down to commit 2eb03376151bb8585caa23ed2673583107bb5193(
>>>> "usb: xhci: Fix slot_id resource race conflict"):
>>>
>>> I see a trivial bug which everyone (myself included tbh) missed before.
>>> Does this help?
>>>
>>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>>> index f11e13f9cdb4..f294032c2ad7 100644
>>> --- a/drivers/usb/host/xhci-mem.c
>>> +++ b/drivers/usb/host/xhci-mem.c
>>> @@ -932,7 +932,7 @@ void xhci_free_virt_device(struct xhci_hcd *xhci, struct xhci_virt_device *dev,
>>>   */
>>> static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
>>> {
>>> -	struct xhci_virt_device *vdev;
>>> +	struct xhci_virt_device *vdev, *tmp_vdev;
>>> 	struct list_head *tt_list_head;
>>> 	struct xhci_tt_bw_info *tt_info, *next;
>>> 	int i;
>>> @@ -952,8 +952,8 @@ static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_i
>>> 		if (tt_info->slot_id == slot_id) {
>>> 			/* are any devices using this tt_info? */
>>> 			for (i = 1; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
>>> -				vdev = xhci->devs[i];
>>> -				if (vdev && (vdev->tt_info == tt_info))
>>> +				tmp_vdev = xhci->devs[i];
>>> +				if (tmp_vdev && (tmp_vdev->tt_info == tt_info))
>>> 					xhci_free_virt_devices_depth_first(
>>> 						xhci, i);
>> 
>> I confirmed this *silly* code is the root cause of this memory leak.
>> And I would suggest simpler code changes (which is what I was testing):
>> 
>> 
>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>> index 81eaad87a3d9..c4a6544aa107 100644
>> --- a/drivers/usb/host/xhci-mem.c
>> +++ b/drivers/usb/host/xhci-mem.c
>> @@ -962,7 +962,7 @@ static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_i
>>   out:
>>          /* we are now at a leaf device */
>>          xhci_debugfs_remove_slot(xhci, slot_id);
>> -       xhci_free_virt_device(xhci, vdev, slot_id);
>> +       xhci_free_virt_device(xhci, xhci->devs[slot_id], slot_id);
>>   }
>>   
>>   int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
>> 
>
>Thanks to both for catching this
>
>I can quickly turn this into a proper patch unless one of you would like to submit one?

Oh, I was not planning to submit a patch at all, since Michał Pecio got the credit of publishing the first patch.

Thanks
David

>
>Thanks
>Mathias