Subject: Re: [RFC PATCH net-next 9/9] ethtool: Add ability to flash transceiver modules' firmware

From: Jakub Kicinski <[email-masked]>
Date: Mon, 22 Jan 2024 21:05:34 -0800

On Mon, 22 Jan 2024 10:45:30 +0200 Danielle Ratson wrote:
>  #include <linux/ethtool.h>
> +#include <linux/sfp.h>
> +#include <linux/firmware.h>

alphabetical order, please

> +static int
> +module_flash_fw_schedule(struct net_device *dev,
> +			 struct ethtool_module_fw_flash_params *params,
> +			 struct netlink_ext_ack *extack)
> +{
> +	const struct ethtool_ops *ops = dev->ethtool_ops;
> +	struct ethtool_module_fw_flash *module_fw;
> +	int err;
> +
> +	if (!ops->set_module_eeprom_by_page ||
> +	    !ops->get_module_eeprom_by_page) {
> +		NL_SET_ERR_MSG(extack,
> +			       "Flashing module firmware is not supported by this device");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (dev->module_fw_flash_in_progress) {
> +		NL_SET_ERR_MSG(extack, "Module firmware flashing already in progress");
> +		return -EBUSY;
> +	}
> +
> +	module_fw = kzalloc(sizeof(*module_fw), GFP_KERNEL);
> +	if (!module_fw)
> +		return -ENOMEM;
> +
> +	module_fw->params = *params;
> +	err = request_firmware(&module_fw->fw, module_fw->params.file_name,

request_firmware_direct() ? I think udev timeout is 30 sec and we're
holding rtnl_lock.. I don't remember why we didn't use that in devlink

> +			       &dev->dev);
> +	if (err) {
> +		NL_SET_ERR_MSG(extack,
> +			       "Failed to request module firmware image");
> +		goto err_request_firmware;
> +	}
> +
> +	err = module_flash_fw_work_init(module_fw, dev, extack);
> +	if (err < 0) {
> +		NL_SET_ERR_MSG(extack,
> +			       "Flashing module firmware is not supported by this device");
> +		goto err_work_init;
> +	}
> +
> +	dev->module_fw_flash_in_progress = true;

What does this protect us from? 

> +static int module_flash_fw(struct net_device *dev, struct nlattr **tb,
> +			   struct netlink_ext_ack *extack)
> +{
> +	struct ethtool_module_fw_flash_params params = {};
> +	struct nlattr *attr;
> +
> +	if (!tb[ETHTOOL_A_MODULE_FW_FLASH_FILE_NAME]) {
> +		NL_SET_ERR_MSG_ATTR(extack,

GENL_REQ_ATTR_CHECK, and you can check it in the caller,
before taking rtnl_lock.

> +				    tb[ETHTOOL_A_MODULE_FW_FLASH_FILE_NAME],
> +				    "File name attribute is missing");
> +		return -EINVAL;
> +	}
> +
> +	params.file_name =
> +		nla_data(tb[ETHTOOL_A_MODULE_FW_FLASH_FILE_NAME]);

Hm. I think you copy the param struct by value to the work container.
nla_data() is in the skb which is going to get freed after _ACT returns.
So if anyone tries to access the name from the work it's going to UAF?

> +
> +	attr = tb[ETHTOOL_A_MODULE_FW_FLASH_PASSWORD];
> +	if (attr) {
> +		params.password = cpu_to_be32(nla_get_u32(attr));
> +		params.password_valid = true;
> +	}
> +
> +	return module_flash_fw_schedule(dev, &params, extack);
> +}