From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleksij Rempel , Sarah Sharp Subject: [ 06/23] xhci: fix null pointer dereference on ring_doorbell_for_active_rings Date: Fri, 2 Aug 2013 18:23:19 +0800 Message-Id: <20130802102037.082023723@linuxfoundation.org> In-Reply-To: <20130802102036.180660415@linuxfoundation.org> References: <20130802102036.180660415@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleksij Rempel 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 Signed-off-by: Sarah Sharp Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -465,7 +465,7 @@ static void ring_doorbell_for_active_rin /* 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; }