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.
This possible bug is found by a static tool developed by myself.
To fix this possible bug, "urb->hcpriv = NULL" should be executed with
holding the lock "hsotg->lock". Because I have no associated hardware,
I cannot test the patch in real execution, and just verify it according
to the code logic.
Fixes: 33ad261aa62b ("usb: dwc2: host: spinlock urb_enqueue")
Signed-off-by: Jia-Ju Bai <baijiaju@xxxxxxxxxxx>
---
v2:
* Add more details in the description.
---
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
