platform/chrome: cros_ec_proto: handle empty payload in getting info legacy

cros_ec_get_proto_info_legacy() expects to receive
sizeof(struct ec_response_hello) from send_command().  The payload is
valid only if the return value is positive.

Return -EPROTO if send_command() returns 0 in
cros_ec_get_proto_info_legacy().

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-13-tzungbi@kernel.org

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 24b8bc30d453c284f1d5a0ec73b9536a4a2b8fa0..60b8ef980b8af7a36c13269ec056465aca2d2edf 100644 (file)
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -356,7 +356,7 @@ static int cros_ec_get_proto_info_legacy(struct cros_ec_device *ec_dev)
        struct cros_ec_command *msg;
        struct ec_params_hello *params;
        struct ec_response_hello *response;
-       int ret;
+       int ret, mapped;
 
        ec_dev->proto_version = 2;
 
@@ -377,12 +377,18 @@ static int cros_ec_get_proto_info_legacy(struct cros_ec_device *ec_dev)
                goto exit;
        }
 
-       ret = cros_ec_map_error(msg->result);
-       if (ret) {
+       mapped = cros_ec_map_error(msg->result);
+       if (mapped) {
+               ret = mapped;
                dev_err(ec_dev->dev, "EC responded to v2 hello with error: %d\n", msg->result);
                goto exit;
        }
 
+       if (ret == 0) {
+               ret = -EPROTO;
+               goto exit;
+       }
+
        response = (struct ec_response_hello *)msg->data;
        if (response->out_data != 0xa1b2c3d4) {
                dev_err(ec_dev->dev,