drivers/message/i2o/i2o_config.c: bound allocation

Fix a case where users can try to allocate arbitarily large amounts of
memory. 64K is overkill for a config request so apply an upper bound.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/message/i2o/i2o_config.c

@@ -188,6 +188,13 @@ static int i2o_cfg_parms(unsigned long arg, unsigned int type)
 	if (!dev)
 		return -ENXIO;
 
+	/*
+	 * Stop users being able to try and allocate arbitary amounts
+	 * of DMA space. 64K is way more than sufficient for this.
+	 */
+	if (kcmd.oplen > 65536)
+		return -EMSGSIZE;
+
 	ops = memdup_user(kcmd.opbuf, kcmd.oplen);
 	if (IS_ERR(ops))
 		return PTR_ERR(ops);