[PATCH v2] usb: dwc2: Fix NULL qh in dwc2_queue_transaction

[Douglas Anderson]

From: Alexandru M Stan <amstan@xxxxxxxxxxxx>

When a usb device disconnects in a certain way, dwc2_queue_transaction
still gets called after dwc2_hcd_cleanup_channels.

dwc2_hcd_cleanup_channels does "channel->qh = NULL;" but
dwc2_queue_transaction still wants to dereference qh.
This adds a check for a null qh.

Signed-off-by: Alexandru M Stan <amstan@xxxxxxxxxxxx>
[dianders: rebased to mainline]
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
While testing a newer version of the Linux kernel on rk3288-veyron
devices we saw a bunch of crashes reported in dwc2_queue_transaction()
where chan->qh was NULL [1].  I don't know how to reproduce those
crashes myself, but I noticed that in our 3.14 kernel we had a patch
that probably fixed it.  That patch was sent upstream ages ago [2] but
never landed.  Here I've rebased the patch.  While I haven't
reproduced the crash myself, it seems fairly likely that this will fix
the problem.

[1] https://crbug.com/1017388
[2] https://lore.kernel.org/r/1442952651-4341-2-git-send-email-amstan@xxxxxxxxxxxx

Changes in v2:
- Rebased to mainline

 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 81afe553aa66..b90f858af960 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -2824,7 +2824,7 @@ static int dwc2_queue_transaction(struct dwc2_hsotg *hsotg,
 		list_move_tail(&chan->split_order_list_entry,
 			       &hsotg->split_order);
 
-	if (hsotg->params.host_dma) {
+	if (hsotg->params.host_dma && chan->qh) {
 		if (hsotg->params.dma_desc_enable) {
 			if (!chan->xfer_started ||
 			    chan->ep_type == USB_ENDPOINT_XFER_ISOC) {
-- 
2.23.0.866.gb869b98d4c-goog