From 10704e2d549484854ace6615fc89cb84f857c01d Mon Sep 17 00:00:00 2001
From: Matt Evans <matt@ozlabs.org>
Date: Tue, 29 Mar 2011 13:40:56 +1100
Subject: [PATCH] --- yaml --- r: 248790 b: refs/heads/master c:
 7ed603ecf8b68ab81f4c83097d3063d43ec73bb8 h: refs/heads/master v: v3

---
 [refs]                        |  2 +-
 trunk/drivers/usb/host/xhci.c | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 379053bcd200..a1ac692b51fa 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 92a3da410aac6e14daaefe13c60368ca28e85830
+refs/heads/master: 7ed603ecf8b68ab81f4c83097d3063d43ec73bb8
diff --git a/trunk/drivers/usb/host/xhci.c b/trunk/drivers/usb/host/xhci.c
index e8ab1899c88e..5c0ae90df31e 100644
--- a/trunk/drivers/usb/host/xhci.c
+++ b/trunk/drivers/usb/host/xhci.c
@@ -2546,6 +2546,17 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
 
 	virt_dev = xhci->devs[udev->slot_id];
 
+	if (WARN_ON(!virt_dev)) {
+		/*
+		 * In plug/unplug torture test with an NEC controller,
+		 * a zero-dereference was observed once due to virt_dev = 0.
+		 * Print useful debug rather than crash if it is observed again!
+		 */
+		xhci_warn(xhci, "Virt dev invalid for slot_id 0x%x!\n",
+			udev->slot_id);
+		return -EINVAL;
+	}
+
 	slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx);
 	/*
 	 * If this is the first Set Address since device plug-in or