From: Oleksij Rempel Date: Sun, 21 Jul 2013 13:36:19 +0000 (+0200) Subject: xhci: fix null pointer dereference on ring_doorbell_for_active_rings X-Git-Tag: firefly_0821_release~176^2~5622^2~15^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d66eaf9f89502971fddcb0de550b01fa6f409d83;p=firefly-linux-kernel-4.4.55.git xhci: fix null pointer dereference on ring_doorbell_for_active_rings 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 Signed-off-by: Sarah Sharp Cc: stable@vger.kernel.org --- diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 1e57eafa6910..5b08cd85f8e7 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -434,7 +434,7 @@ static void ring_doorbell_for_active_rings(struct xhci_hcd *xhci, /* 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; }