linux-kernel - [ 35/91] USB: cdc-wdm: remove from device list on disconnect

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Date:	Sun, 27 May 2012 09:25:41 +0900
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Oliver Neukum <oliver@...kum.org>,
	Bjørn Mork <bjorn@...k.no>
Subject: [ 35/91] USB: cdc-wdm: remove from device list on disconnect

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bjørn Mork <bjorn@...k.no>

commit 6286d85e8efdb59252d1ceb99a56fa6b0b11526c upstream.

Prevents dereferencing an invalid struct usb_interface
pointer.

Always delete entry from device list whether or not the
rest of the device state cleanup is postponed. The device
list uses desc->intf as key, and wdm_open will dereference
this key while searching for a matching device.  A device
should not appear in the list unless probe() has succeeded
and disconnect() has not finished.

Cc: Oliver Neukum <oliver@...kum.org>
Signed-off-by: Bjørn Mork <bjorn@...k.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/class/cdc-wdm.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -309,9 +309,6 @@ static void free_urbs(struct wdm_device
 
 static void cleanup(struct wdm_device *desc)
 {
-	spin_lock(&wdm_device_list_lock);
-	list_del(&desc->device_list);
-	spin_unlock(&wdm_device_list_lock);
 	kfree(desc->sbuf);
 	kfree(desc->inbuf);
 	kfree(desc->orq);
@@ -778,6 +775,9 @@ static int wdm_create(struct usb_interfa
 out:
 	return rv;
 err:
+	spin_lock(&wdm_device_list_lock);
+	list_del(&desc->device_list);
+	spin_unlock(&wdm_device_list_lock);
 	cleanup(desc);
 	return rv;
 }
@@ -903,6 +903,12 @@ static void wdm_disconnect(struct usb_in
 	cancel_work_sync(&desc->rxwork);
 	mutex_unlock(&desc->wlock);
 	mutex_unlock(&desc->rlock);
+
+	/* the desc->intf pointer used as list key is now invalid */
+	spin_lock(&wdm_device_list_lock);
+	list_del(&desc->device_list);
+	spin_unlock(&wdm_device_list_lock);
+
 	if (!desc->count)
 		cleanup(desc);
 	mutex_unlock(&wdm_mutex);


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