[PATCH 3.14 12/35] usb: xhci: Fix panic if disconnect

Greg Kroah-Hartman
2016-09-05T17:49:17Z

From: Jim Lin <jilin@nvidia.com>

commit 88716a93766b8f095cdef37a8e8f2c93aa233b21 upstream.

After a device is disconnected, xhci_stop_device() will be invoked
in xhci_bus_suspend().
Also the "disconnect" IRQ will have ISR to invoke
xhci_free_virt_device() in this sequence.
xhci_irq -> xhci_handle_event -> handle_cmd_completion ->
xhci_handle_cmd_disable_slot -> xhci_free_virt_device

If xhci->devs[slot_id] has been assigned to NULL in
xhci_free_virt_device(), then virt_dev->eps[i].ring in
xhci_stop_device() may point to an invlid address to cause kernel
panic.

virt_dev = xhci->devs[slot_id];
:
if (virt_dev->eps[i].ring && virt_dev->eps[i].ring->dequeue)

[] Unable to handle kernel paging request at virtual address 00001a68
[] pgd=ffffffc001430000
[] [00001a68] *pgd=000000013c807003, *pud=000000013c807003,
*pmd=000000013c808003, *pte=0000000000000000
[] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[] CPU: 0 PID: 39 Comm: kworker/0:1 Tainted: G U
[] Workqueue: pm pm_runtime_work
[] task: ffffffc0bc0e0bc0 ti: ffffffc0bc0ec000 task.ti:
ffffffc0bc0ec000
[] PC is at xhci_stop_device.constprop.11+0xb4/0x1a4

This issue is found when running with realtek ethernet device
(0bda:8153).

Signed-off-by: Jim Lin <jilin@nvidia.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/host/xhci-hub.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -276,6 +276,9 @@ static int xhci_stop_device(struct xhci_

ret = 0;
virt_dev = xhci->devs[slot_id];
+ if (!virt_dev)
+ return -ENODEV;
+
cmd = xhci_alloc_command(xhci, false, true, GFP_NOIO);
if (!cmd) {
xhci_dbg(xhci, "Couldn't allocate command structure.\n");