USB: resizing usbmon binary interface buffer causes protection faults

commit 33d973a upstream.

Enlarging the buffer size via the MON_IOCT_RING_SIZE ioctl causes
general protection faults. It appears the culprit is an incorrect
argument to mon_free_buff: instead of passing the size of the current
buffer being freed, the size of the new buffer is passed.

Use the correct size argument to mon_free_buff when changing the size of
the buffer.

Signed-off-by: Steven Robertson <steven@strobe.cc>
Acked-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/mon/mon_bin.c

@@ -1010,7 +1010,7 @@ static int mon_bin_ioctl(struct inode *inode, struct file *file,
 
 		mutex_lock(&rp->fetch_lock);
 		spin_lock_irqsave(&rp->b_lock, flags);
-		mon_free_buff(rp->b_vec, size/CHUNK_SIZE);
+		mon_free_buff(rp->b_vec, rp->b_size/CHUNK_SIZE);
 		kfree(rp->b_vec);
 		rp->b_vec  = vec;
 		rp->b_size = size;