thunderbolt: Limit XDomain response copy to actual frame size

tb_xdomain_copy() copies req->response_size bytes from the received
packet buffer regardless of the actual frame size.  When a short
response arrives, this reads past the valid frame data in the DMA
pool buffer into stale contents from previous transactions.

Use the minimum of frame size and expected response size for the
copy length.

Fixes: cdae7c07e3 ("thunderbolt: Add support for XDomain properties")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/xdomain.c

@@ -123,7 +123,9 @@ static bool tb_xdomain_match(const struct tb_cfg_request *req,
 static bool tb_xdomain_copy(struct tb_cfg_request *req,
 			    const struct ctl_pkg *pkg)
 {
-	memcpy(req->response, pkg->buffer, req->response_size);
+	size_t len = min_t(size_t, pkg->frame.size, req->response_size);
+
+	memcpy(req->response, pkg->buffer, len);
 	req->result.err = 0;
 	return true;
 }