3.16.50-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> commit 4b895868bb2da60a386a17cde3bf9ecbc70c79f4 upstream. This off by one in stream_id indexing caused NULL pointer dereference and soft lockup on machines with USB attached SCSI devices connected to a hotpluggable xhci controller. The code that cleans up pending URBs for dead hosts tried to dereference a stream ring at the invalid stream_id 0. ep->stream_info->stream_rings[0] doesn't point to a ring. Start looping stream_id from 1 like in all the other places in the driver, and check that the ring exists before trying to kill URBs on it. Reported-by: rocko r <rockorequin@xxxxxxxxx> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- drivers/usb/host/xhci-ring.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -821,13 +821,16 @@ static void xhci_kill_endpoint_urbs(stru (ep->ep_state & EP_GETTING_NO_STREAMS)) { int stream_id; - for (stream_id = 0; stream_id < ep->stream_info->num_streams; + for (stream_id = 1; stream_id < ep->stream_info->num_streams; stream_id++) { + ring = ep->stream_info->stream_rings[stream_id]; + if (!ring) + continue; + xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb, "Killing URBs for slot ID %u, ep index %u, stream %u", - slot_id, ep_index, stream_id + 1); - xhci_kill_ring_urbs(xhci, - ep->stream_info->stream_rings[stream_id]); + slot_id, ep_index, stream_id); + xhci_kill_ring_urbs(xhci, ring); } } else { ring = ep->ring;