[PATCH] usb: dwc2: gadget: avoid null dereference on incomplete transfer

[John Keeping <john@metanate.com>]

Setting up a gadget with the uac2 function results in:

  Unable to handle kernel NULL pointer dereference at virtual address 00000058
  ...
  PC is at dwc2_hsotg_irq+0x7f0/0x908
  LR is at dwc2_hsotg_irq+0x4c/0x908
  Backtrace:
  [<c03cd5fc>] (dwc2_hsotg_irq) from [<c00814fc>] (handle_irq_event_percpu+0x130/0x3ec)
  [<c00813cc>] (handle_irq_event_percpu) from [<c0081800>] (handle_irq_event+0x48/0x6c)

In all other loops we already skip endpoints that are null, so do so
here as well.

Signed-off-by: John Keeping <john@metanate.com>
---
 drivers/usb/dwc2/gadget.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 0abf73c..df43ec0 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -2606,7 +2606,9 @@ irq_retry:
 		for (idx = 1; idx < hsotg->num_of_eps; idx++) {
 			hs_ep = hsotg->eps_in[idx];
 
-			if (!hs_ep->isochronous || hs_ep->has_correct_parity)
+			if (!hs_ep ||
+			    !hs_ep->isochronous ||
+			    hs_ep->has_correct_parity)
 				continue;
 
 			epctl_reg = DIEPCTL(idx);
@@ -2623,7 +2625,9 @@ irq_retry:
 		for (idx = 1; idx < hsotg->num_of_eps; idx++) {
 			hs_ep = hsotg->eps_out[idx];
 
-			if (!hs_ep->isochronous || hs_ep->has_correct_parity)
+			if (!hs_ep ||
+			    !hs_ep->isochronous ||
+			    hs_ep->has_correct_parity)
 				continue;
 
 			epctl_reg = DOEPCTL(idx);
-- 
2.7.0.226.gfe986fe