cxl/mbox: Add a check on input payload size

A bug in the LSA code resulted in transfers slightly larger
than the mailbox size. Let us make it easier to catch similar
issues in future by adding a low level check.
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20220815154044.24733-2-Jonathan.Cameron@huawei.comSigned-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -174,7 +174,7 @@ int cxl_mbox_send_cmd(struct cxl_dev_state *cxlds, u16 opcode, void *in,
 	};
 	int rc;
 
-	if (out_size > cxlds->payload_size)
+	if (in_size > cxlds->payload_size || out_size > cxlds->payload_size)
 		return -E2BIG;
 
 	rc = cxlds->mbox_send(cxlds, &mbox_cmd);