devlink: validate length of param values

DEVLINK_ATTR_PARAM_VALUE_DATA may have different types
so it's not checked by the normal netlink policy. Make
sure the attribute length is what we expect.

Fixes: e3b7ca18 ("devlink: Add param set command")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/devlink.c

@@ -3352,34 +3352,41 @@ devlink_param_value_get_from_info(const struct devlink_param *param,
 				  struct genl_info *info,
 				  union devlink_param_value *value)
 {
+	struct nlattr *param_data;
 	int len;
 
-	if (param->type != DEVLINK_PARAM_TYPE_BOOL &&
-	    !info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA])
+	param_data = info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA];
+
+	if (param->type != DEVLINK_PARAM_TYPE_BOOL && !param_data)
 		return -EINVAL;
 
 	switch (param->type) {
 	case DEVLINK_PARAM_TYPE_U8:
-		value->vu8 = nla_get_u8(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]);
+		if (nla_len(param_data) != sizeof(u8))
+			return -EINVAL;
+		value->vu8 = nla_get_u8(param_data);
 		break;
 	case DEVLINK_PARAM_TYPE_U16:
-		value->vu16 = nla_get_u16(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]);
+		if (nla_len(param_data) != sizeof(u16))
+			return -EINVAL;
+		value->vu16 = nla_get_u16(param_data);
 		break;
 	case DEVLINK_PARAM_TYPE_U32:
-		value->vu32 = nla_get_u32(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]);
+		if (nla_len(param_data) != sizeof(u32))
+			return -EINVAL;
+		value->vu32 = nla_get_u32(param_data);
 		break;
 	case DEVLINK_PARAM_TYPE_STRING:
-		len = strnlen(nla_data(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]),
-			      nla_len(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]));
-		if (len == nla_len(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]) ||
+		len = strnlen(nla_data(param_data), nla_len(param_data));
+		if (len == nla_len(param_data) ||
 		    len >= __DEVLINK_PARAM_MAX_STRING_VALUE)
 			return -EINVAL;
-		strcpy(value->vstr,
-		       nla_data(info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA]));
+		strcpy(value->vstr, nla_data(param_data));
 		break;
 	case DEVLINK_PARAM_TYPE_BOOL:
-		value->vbool = info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA] ?
-			       true : false;
+		if (param_data && nla_len(param_data))
+			return -EINVAL;
+		value->vbool = nla_get_flag(param_data);
 		break;
 	}
 	return 0;