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Message-ID: <e8ee2457-0d43-834c-8bdb-69791dc9fc34@buaa.edu.cn>
Date: Mon, 25 Sep 2023 18:11:05 +0800
From: Jia-Ju Bai <baijiaju@...a.edu.cn>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: hminas@...opsys.com, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: dwc2: fix possible NULL pointer dereference caused
by driver concurrency
Thanks for the reply :)
On 2023/9/25 17:38, Greg KH wrote:
> On Mon, Sep 25, 2023 at 05:17:41PM +0800, Jia-Ju Bai wrote:
>> In _dwc2_hcd_urb_enqueue(), "urb->hcpriv = NULL" is executed without
>> holding the lock "hsotg->lock". In _dwc2_hcd_urb_dequeue():
>>
>> spin_lock_irqsave(&hsotg->lock, flags);
>> ...
>> if (!urb->hcpriv) {
>> dev_dbg(hsotg->dev, "## urb->hcpriv is NULL ##\n");
>> goto out;
>> }
>> rc = dwc2_hcd_urb_dequeue(hsotg, urb->hcpriv); // Use urb->hcpriv
>> ...
>> out:
>> spin_unlock_irqrestore(&hsotg->lock, flags);
>>
>> When _dwc2_hcd_urb_enqueue() and _dwc2_hcd_urb_dequeue() are
>> concurrently executed, the NULL check of "urb->hcpriv" can be executed
>> before "urb->hcpriv = NULL". After urb->hcpriv is NULL, it can be used
>> in the function call to dwc2_hcd_urb_dequeue(), which can cause a NULL
>> pointer dereference.
> Odd trailing spaces in your changelog text, is that intentional?
They are caused by the configuration of my file editor, and I changed it
just now.
>
>> To fix this possible bug, "urb->hcpriv = NULL" should be executed with
>> holding the lock "hsotg->lock".
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju@...a.edu.cn>
>> ---
>> drivers/usb/dwc2/hcd.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
>> index 657f1f659ffa..35c7a4df8e71 100644
>> --- a/drivers/usb/dwc2/hcd.c
>> +++ b/drivers/usb/dwc2/hcd.c
>> @@ -4769,8 +4769,8 @@ static int _dwc2_hcd_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
>> if (qh_allocated && qh->channel && qh->channel->qh == qh)
>> qh->channel->qh = NULL;
>> fail2:
>> - spin_unlock_irqrestore(&hsotg->lock, flags);
>> urb->hcpriv = NULL;
>> + spin_unlock_irqrestore(&hsotg->lock, flags);
>> kfree(qtd);
>> fail1:
>> if (qh_allocated) {
>> --
>> 2.34.1
>>
> What commit id does this fix?
>
> And how did you test this to verify it works properly?
>
> And how was it found?
I sent a v2 patch to add these details and fix the mistakes about
trailing spaces.
Thanks,
Jia-Ju Bai
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