Patch "usb: xhci: Fix panic if disconnect" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

usb: xhci: Fix panic if disconnect

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-xhci-fix-panic-if-disconnect.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jim Lin <[email protected]>
Date: Tue, 16 Aug 2016 10:18:05 +0300
Subject: usb: xhci: Fix panic if disconnect

From: Jim Lin <[email protected]>

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).

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

@@ -377,6 +377,9 @@ 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");

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/usb-xhci-fix-panic-if-disconnect.patch