linux-kernel - Re: Null Pointer BUG in uhci

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Date:	Tue, 7 Jul 2009 11:10:33 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Jiri Kosina <jkosina@...e.cz>,
	"Michael S. Zick" <lkml@...ethan.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: Null Pointer BUG in uhci_hcd

On Tue, 7 Jul 2009, Oliver Neukum wrote:

> Am Dienstag, 7. Juli 2009 11:13:01 schrieb Jiri Kosina:
> > [ adding linux-usb to CC ]
> >
> > On Sun, 5 Jul 2009, Michael S. Zick wrote:
> > > Anyone with suggestions about this one?
> 
> Looks like we should test for presence before we switch off
> autosuspend for khubd. Please test this diagnostic patch if this is
> repeatable.

That patch won't fix the problem.  This issue is not that hdev is NULL; 
the problem is that the hub driver isn't bound to hdev and as a result, 
the hdev_to_hub routine fails.

This patch may work better.

Alan Stern


Index: usb-2.6/drivers/usb/core/hub.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/hub.c
+++ usb-2.6/drivers/usb/core/hub.c
@@ -163,8 +163,10 @@ static inline char *portspeed(int portst
 }
 
 /* Note that hdev or one of its children must be locked! */
-static inline struct usb_hub *hdev_to_hub(struct usb_device *hdev)
+static struct usb_hub *hdev_to_hub(struct usb_device *hdev)
 {
+	if (!hdev || !hdev->actconfig)
+		return NULL;
 	return usb_get_intfdata(hdev->actconfig->interface[0]);
 }
 
@@ -385,8 +387,10 @@ static void kick_khubd(struct usb_hub *h
 
 void usb_kick_khubd(struct usb_device *hdev)
 {
-	/* FIXME: What if hdev isn't bound to the hub driver? */
-	kick_khubd(hdev_to_hub(hdev));
+	struct usb_hub *hub = hdev_to_hub(hdev);
+
+	if (hub)
+		kick_khubd(hub);
 }
 
 

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