[PATCH 3/7] xhci: Fix null pointer dereference when host dies

[Mathias Nyman <mathias.nyman@linux.intel.com>]

Make sure xhci_free_dev() and xhci_kill_endpoint_urbs() do not race
and cause null pointer dereference when host suddenly dies.

Usb core may call xhci_free_dev() which frees the xhci->devs[slot_id]
virt device at the same time that xhci_kill_endpoint_urbs() tries to
loop through all the device's endpoints, checking if there are any
cancelled urbs left to give back.

hold the xhci spinlock while freeing the virt device

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 79d7931c048a..50b41213e827 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3974,6 +3974,7 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct usb_device *udev)
 	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
 	struct xhci_virt_device *virt_dev;
 	struct xhci_slot_ctx *slot_ctx;
+	unsigned long flags;
 	int i, ret;
 
 	/*
@@ -4000,7 +4001,11 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct usb_device *udev)
 		virt_dev->eps[i].ep_state &= ~EP_STOP_CMD_PENDING;
 	virt_dev->udev = NULL;
 	xhci_disable_slot(xhci, udev->slot_id);
+
+	spin_lock_irqsave(&xhci->lock, flags);
 	xhci_free_virt_device(xhci, udev->slot_id);
+	spin_unlock_irqrestore(&xhci->lock, flags);
+
 }
 
 int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id)
-- 
2.25.1