staging: greybus: Check for string truncation instead of NUL-termination

Commit 18f44de63f88 ("staging: greybus: change strncpy() to
strscpy_pad()") didn't remove the now unnecessary NUL-termination
checks. Unlike strncpy(), strscpy_pad() guarantees that the destination
buffer is NUL-terminated, making these checks obsolete. Remove them and
check for string truncation instead.

Compile-tested only.

Signed-off-by: Thorsten Blum <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/greybus/fw-management.c

···
 	fw_info->major = le16_to_cpu(response.major);
 	fw_info->minor = le16_to_cpu(response.minor);
 
-	strscpy_pad(fw_info->firmware_tag, response.firmware_tag);
-
-	/*
-	 * The firmware-tag should be NULL terminated, otherwise throw error but
-	 * don't fail.
-	 */
-	if (fw_info->firmware_tag[GB_FIRMWARE_TAG_MAX_SIZE - 1] != '\0') {
+	ret = strscpy_pad(fw_info->firmware_tag, response.firmware_tag);
+	if (ret == -E2BIG)
 		dev_err(fw_mgmt->parent,
-			"fw-version: firmware-tag is not NULL terminated\n");
-		fw_info->firmware_tag[GB_FIRMWARE_TAG_MAX_SIZE - 1] = '\0';
-	}
+			"fw-version: truncated firmware tag: %s\n",
+			fw_info->firmware_tag);
 
 	return 0;
 }
···
 	}
 
 	request.load_method = load_method;
-	strscpy_pad(request.firmware_tag, tag);
 
-	/*
-	 * The firmware-tag should be NULL terminated, otherwise throw error and
-	 * fail.
-	 */
-	if (request.firmware_tag[GB_FIRMWARE_TAG_MAX_SIZE - 1] != '\0') {
-		dev_err(fw_mgmt->parent, "load-and-validate: firmware-tag is not NULL terminated\n");
+	ret = strscpy_pad(request.firmware_tag, tag);
+	if (ret == -E2BIG) {
+		dev_err(fw_mgmt->parent,
+			"load-and-validate: truncated firmware tag: %s\n",
+			request.firmware_tag);
 		return -EINVAL;
 	}
 
···
 	struct gb_fw_mgmt_backend_fw_version_response response;
 	int ret;
 
-	strscpy_pad(request.firmware_tag, fw_info->firmware_tag);
-
-	/*
-	 * The firmware-tag should be NULL terminated, otherwise throw error and
-	 * fail.
-	 */
-	if (request.firmware_tag[GB_FIRMWARE_TAG_MAX_SIZE - 1] != '\0') {
-		dev_err(fw_mgmt->parent, "backend-version: firmware-tag is not NULL terminated\n");
+	ret = strscpy_pad(request.firmware_tag, fw_info->firmware_tag);
+	if (ret == -E2BIG) {
+		dev_err(fw_mgmt->parent,
+			"backend-fw-version: truncated firmware tag: %s\n",
+			request.firmware_tag);
 		return -EINVAL;
 	}
 
···
 	int ret;
 
 	ret = strscpy_pad(request.firmware_tag, tag);
-
-	/*
-	 * The firmware-tag should be NULL terminated, otherwise throw error and
-	 * fail.
-	 */
 	if (ret == -E2BIG) {
-		dev_err(fw_mgmt->parent, "backend-update: firmware-tag is not NULL terminated\n");
+		dev_err(fw_mgmt->parent,
+			"backend-fw-update: truncated firmware tag: %s\n",
+			request.firmware_tag);
 		return -EINVAL;
 	}