xhci: fix null pointer dereference on ring_doorbell_for_active_rings
commit d66eaf9f89502971fddcb0de550b01fa6f409d83 upstream.
in some cases where device is attched to xhci port and do not responding,
for example ath9k_htc with stalled firmware, kernel will
crash on ring_doorbell_for_active_rings.
This patch check if pointer exist before it is used.
This patch should be backported to kernels as old as 2.6.35, that
contain the commit e9df17eb1408cfafa3d1844bfc7f22c7237b31b8 "USB: xhci:
Correct assumptions about number of rings per endpoint"
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 17eea8f..ac0e346 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -426,7 +426,7 @@
/* A ring has pending URBs if its TD list is not empty */
if (!(ep->ep_state & EP_HAS_STREAMS)) {
- if (!(list_empty(&ep->ring->td_list)))
+ if (ep->ring && !(list_empty(&ep->ring->td_list)))
xhci_ring_ep_doorbell(xhci, slot_id, ep_index, 0);
return;
}
