Move the spin_unlock_irqrestore in _dwc2_hcd_urb_enqueue() · Pull Request !2336 · openEuler/kernel

Hello, I am Haoran Zheng from School of Cyber Science and Technology in Beihang University. I find a possible bug, using a program analysis tool named BassCheck developed by our team.

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.

To fix this possible bug, "urb->hcpriv = NULL" should be executed with holding the lock "hsotg->lock". After using this patch, my tool never reports the possible bug, with the kernelconfiguration allyesconfig for x86_64. Because I have no associated hardware, I cannot test the patch in runtime testing, and just verify it according to the code logic.

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