xhci: Limit roothub ports to 15 USB3 & 31 USB2 ports.

The USB core allocates a USB 2.0 roothub descriptor that has room for 31
(USB_MAXCHILDREN) ports' worth of DeviceRemovable and PortPwrCtrlMask
fields.  Limit the number of USB 2.0 roothub ports accordingly.  I don't
expect to run into this limitation ever, but this prevents a buffer
overflow issue in the roothub descriptor filling code.

Similarly, a USB 3.0 hub can only have 15 downstream ports, so limit the
USB 3.0 roothub to 15 USB 3.0 ports.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 180a2abbc868..71fd8bd287fe 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1803,6 +1803,20 @@ static int xhci_setup_port_arrays(struct xhci_hcd *xhci, gfp_t flags)
         }
         xhci_dbg(xhci, "Found %u USB 2.0 ports and %u USB 3.0 ports.\n",
                         xhci->num_usb2_ports, xhci->num_usb3_ports);
+
+        /* Place limits on the number of roothub ports so that the hub
+         * descriptors aren't longer than the USB core will allocate.
+         */
+        if (xhci->num_usb3_ports > 15) {
+                xhci_dbg(xhci, "Limiting USB 3.0 roothub ports to 15.\n");
+                xhci->num_usb3_ports = 15;
+        }
+        if (xhci->num_usb2_ports > USB_MAXCHILDREN) {
+                xhci_dbg(xhci, "Limiting USB 2.0 roothub ports to %u.\n",
+                                USB_MAXCHILDREN);
+                xhci->num_usb2_ports = USB_MAXCHILDREN;
+        }
+
         /*
          * Note we could have all USB 3.0 ports, or all USB 2.0 ports.
          * Not sure how the USB core will handle a hub with no ports...
@@ -1827,6 +1841,8 @@ static int xhci_setup_port_arrays(struct xhci_hcd *xhci, gfp_t flags)
                                         "addr = %p\n", i,
                                         xhci->usb2_ports[port_index]);
                         port_index++;
+                        if (port_index == xhci->num_usb2_ports)
+                                break;
                 }
         }
         if (xhci->num_usb3_ports) {
@@ -1845,6 +1861,8 @@ static int xhci_setup_port_arrays(struct xhci_hcd *xhci, gfp_t flags)
                                                 "addr = %p\n", i,
                                                 xhci->usb3_ports[port_index]);
                                 port_index++;
+                                if (port_index == xhci->num_usb3_ports)
+                                        break;
                         }
         }
         return 0;