[PATCH] [238/275] USB: cdc-acm: fix potential null-pointer dereference on disconnect

[Andi Kleen]

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Johan Hovold <jhovold@xxxxxxxxx>

commit 7e7797e7f6f7bfab73fca02c65e40eaa5bb9000c upstream.

Fix potential null-pointer exception on disconnect introduced by commit
11ea859d64b69a747d6b060b9ed1520eab1161fe (USB: additional power savings
for cdc-acm devices that support remote wakeup).

Only access acm->dev after making sure it is non-null in control urb
completion handler.

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

---
 drivers/usb/class/cdc-acm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.35.y/drivers/usb/class/cdc-acm.c
===================================================================
--- linux-2.6.35.y.orig/drivers/usb/class/cdc-acm.c	2011-03-29 23:03:03.154219461 -0700
+++ linux-2.6.35.y/drivers/usb/class/cdc-acm.c	2011-03-29 23:03:03.173218975 -0700
@@ -297,6 +297,8 @@
 	if (!ACM_READY(acm))
 		goto exit;
 
+	usb_mark_last_busy(acm->dev);
+
 	data = (unsigned char *)(dr + 1);
 	switch (dr->bNotificationType) {
 	case USB_CDC_NOTIFY_NETWORK_CONNECTION:
@@ -336,7 +338,6 @@
 		break;
 	}
 exit:
-	usb_mark_last_busy(acm->dev);
 	retval = usb_submit_urb(urb, GFP_ATOMIC);
 	if (retval)
 		dev_err(&urb->dev->dev, "%s - usb_submit_urb failed with "
--
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