[PATCH v4 05/11] firewall: introduce stm32_firewall framework

[Gatien CHEVALLIER]

On 8/12/23 16:09, Simon Horman wrote:
> On Fri, Aug 11, 2023 at 12:07:25PM +0200, Gatien Chevallier wrote:
> 
> ...
> 
>> diff --git a/drivers/bus/stm32_firewall.c b/drivers/bus/stm32_firewall.c
>> new file mode 100644
>> index 000000000000..900f3b052a66
>> --- /dev/null
>> +++ b/drivers/bus/stm32_firewall.c
>> @@ -0,0 +1,293 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2023, STMicroelectronics - All Rights Reserved
>> + */
>> +
>> +#include <linux/bitfield.h>
>> +#include <linux/bits.h>
>> +#include <linux/bus/stm32_firewall_device.h>
>> +#include <linux/device.h>
>> +#include <linux/err.h>
>> +#include <linux/init.h>
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/types.h>
>> +#include <linux/slab.h>
>> +
>> +#include "stm32_firewall.h"
>> +
>> +/* Corresponds to STM32_FIREWALL_MAX_EXTRA_ARGS + firewall ID */
>> +#define STM32_FIREWALL_MAX_ARGS		(STM32_FIREWALL_MAX_EXTRA_ARGS + 1)
>> +
>> +static LIST_HEAD(firewall_controller_list);
>> +static DEFINE_MUTEX(firewall_controller_list_lock);
>> +
>> +/* Firewall device API */
>> +int stm32_firewall_get_firewall(struct device_node *np, struct stm32_firewall *firewall,
>> +				unsigned int nb_firewall)
>> +{
>> +	struct stm32_firewall_controller *ctrl;
>> +	struct of_phandle_iterator it;
>> +	unsigned int i, j = 0;
>> +	int err;
>> +
>> +	if (!firewall || !nb_firewall)
>> +		return -EINVAL;
>> +
>> +	/* Parse property with phandle parsed out */
>> +	of_for_each_phandle(&it, err, np, "feature-domains", "#feature-domain-cells", 0) {
>> +		struct of_phandle_args provider_args;
>> +		struct device_node *provider = it.node;
>> +		const char *fw_entry;
>> +		bool match = false;
>> +
>> +		if (err) {
>> +			pr_err("Unable to get feature-domains property for node %s\n, err: %d",
>> +			       np->full_name, err);
>> +			of_node_put(provider);
>> +			return err;
>> +		}
>> +
>> +		if (j > nb_firewall) {
>> +			pr_err("Too many firewall controllers");
>> +			of_node_put(provider);
>> +			return -EINVAL;
>> +		}
>> +
>> +		provider_args.args_count = of_phandle_iterator_args(&it, provider_args.args,
>> +								    STM32_FIREWALL_MAX_ARGS);
>> +
>> +		/* Check if the parsed phandle corresponds to a registered firewall controller */
>> +		mutex_lock(&firewall_controller_list_lock);
>> +		list_for_each_entry(ctrl, &firewall_controller_list, entry) {
>> +			if (ctrl->dev->of_node->phandle == it.phandle) {
>> +				match = true;
>> +				firewall[j].firewall_ctrl = ctrl;
>> +				break;
>> +			}
>> +		}
>> +		mutex_unlock(&firewall_controller_list_lock);
>> +
>> +		if (!match) {
>> +			firewall[j].firewall_ctrl = NULL;
>> +			pr_err("No firewall controller registered for %s\n", np->full_name);
>> +			of_node_put(provider);
>> +			return -ENODEV;
>> +		}
>> +
>> +		err = of_property_read_string_index(np, "feature-domain-names", j, &fw_entry);
>> +		if (err == 0)
>> +			firewall[j].entry = fw_entry;
>> +
>> +		/* Handle the case when there are no arguments given along with the phandle */
>> +		if (provider_args.args_count < 0 ||
>> +		    provider_args.args_count > STM32_FIREWALL_MAX_ARGS) {
>> +			of_node_put(provider);
>> +			return -EINVAL;
>> +		} else if (provider_args.args_count == 0) {
>> +			firewall[j].extra_args_size = 0;
>> +			firewall[j].firewall_id = U32_MAX;
>> +			j++;
>> +			continue;
>> +		}
>> +
>> +		/* The firewall ID is always the first argument */
>> +		firewall[j].firewall_id = provider_args.args[0];
>> +
>> +		/* Extra args start at the third argument */
>> +		for (i = 0; i < provider_args.args_count; i++)
>> +			firewall[j].extra_args[i] = provider_args.args[i + 1];
> 
> Hi Gatien,
> 
> Above it is checked that the maximum value of provider_args.args_count is
> STM32_FIREWALL_MAX_ARGS.
> So here the maximum value of i is STM32_FIREWALL_MAX_ARGS - 1.
> 
> STM32_FIREWALL_MAX_ARGS is defined as STM32_FIREWALL_MAX_EXTRA_ARGS + 1
> And STM32_FIREWALL_MAX_EXTRA_ARGS is defined as 5.
> So the maximum value of i is (5 + 1 - 1) = 5.
> 
> firewall[j] is of type struct stm32_firewall.
> And its args field has STM32_FIREWALL_MAX_EXTRA_ARGS (5) elements.
> Thus the maximum valid index is (5 - 1) = 4.
> 
> But the line above may access index 5.
> 
> Flagged by Smatch.
> 

Hi Simon,

Thank you for pointing this out.

I'll correct it for V5.

Best regards,
Gatien
>> +
>> +		/* Remove the firewall ID arg that is not an extra argument */
>> +		firewall[j].extra_args_size = provider_args.args_count - 1;
>> +
>> +		j++;
>> +	}
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(stm32_firewall_get_firewall);
> 
> ...
> 
>> diff --git a/include/linux/bus/stm32_firewall_device.h b/include/linux/bus/stm32_firewall_device.h
>> new file mode 100644
>> index 000000000000..7b4450a8ec15
>> --- /dev/null
>> +++ b/include/linux/bus/stm32_firewall_device.h
>> @@ -0,0 +1,141 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2023, STMicroelectronics - All Rights Reserved
>> + */
>> +
>> +#ifndef STM32_FIREWALL_DEVICE_H
>> +#define STM32_FIREWALL_DEVICE_H
>> +
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/types.h>
>> +
>> +#define STM32_FIREWALL_MAX_EXTRA_ARGS		5
>> +
>> +/* Opaque reference to stm32_firewall_controller */
>> +struct stm32_firewall_controller;
>> +
>> +/**
>> + * struct stm32_firewall - Information on a device's firewall. Each device can have more than one
>> + *			   firewall.
>> + *
>> + * @firewall_ctrl:		Pointer referencing a firewall controller of the device. It is
>> + *				opaque so a device cannot manipulate the controller's ops or access
>> + *				the controller's data
>> + * @extra_args:			Extra arguments that are implementation dependent
>> + * @entry:			Name of the firewall entry
>> + * @extra_args_size:		Number of extra arguments
>> + * @firewall_id:		Firewall ID associated the device for this firewall controller
>> + */
>> +struct stm32_firewall {
>> +	struct stm32_firewall_controller *firewall_ctrl;
>> +	u32 extra_args[STM32_FIREWALL_MAX_EXTRA_ARGS];
>> +	const char *entry;
>> +	size_t extra_args_size;
>> +	u32 firewall_id;
>> +};
> 
> ...