linux-kernel - Re: [PATCH V5 01/16] rv: Add Runtime Verification (RV) interface

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Message-ID: <3758d3bd-7272-e907-a51a-44a21d757674@kernel.org>
Date:   Fri, 15 Jul 2022 13:47:28 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Tao Zhou <tao.zhou@...ux.dev>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Gabriele Paoloni <gpaoloni@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH V5 01/16] rv: Add Runtime Verification (RV) interface

On 7/14/22 09:46, Tao Zhou wrote:
> On Wed, Jul 13, 2022 at 11:17:17PM +0200,
> Daniel Bristot de Oliveira <bristot@...nel.org> wrote:
> 
> [...]
> 
>> +void put_task_monitor_slot(int slot)
>> +{
>> +	lockdep_assert_held(&rv_interface_lock);
>> +
>> +	if (slot < 0 || slot > RV_PER_TASK_MONITORS) {
> 
> slot is the array index that should be 0 here. The up bound is not bigger
> than 0 because the element of array now is RV_PER_TASK_MONITORS. 
> 
> So up bound check is 'slot > RV_PER_TASK_MONITORS-1'.

fixed! (slot >= RV...)

> [...]
> 
>> +/*
>> + * interface for enabling/disabling a monitor.
>> + */
>> +static ssize_t monitor_enable_write_data(struct file *filp, const char __user *user_buf,
>> +					 size_t count, loff_t *ppos)
>> +{
>> +	struct rv_monitor_def *mdef = filp->private_data;
>> +	int retval;
>> +	bool val;
>> +
>> +	retval = kstrtobool_from_user(user_buf, count, &val);
>> +	if (retval)
>> +		return retval;
>> +
>> +	retval = count;
>> +
>> +	mutex_lock(&rv_interface_lock);
>> +
>> +	if (val)
>> +		retval = enable_monitor(mdef);
>> +	else
>> +		retval = disable_monitor(mdef);
>> +
>> +	mutex_unlock(&rv_interface_lock);
>> +
>> +	return retval ? retval : count;
> 
> Feel that this can be written `return retval ? : count;`


why not...

> [...]
> 
>> +static void *enabled_monitors_start(struct seq_file *m, loff_t *pos)
>> +{
>> +	struct rv_monitor_def *m_def;
>> +	loff_t l;
>> +
>> +	mutex_lock(&rv_interface_lock);
>> +
>> +	if (list_empty(&rv_monitors_list))
>> +		return NULL;
>> +
>> +	m_def = list_entry(&rv_monitors_list, struct rv_monitor_def, list);
>> +
>> +	for (l = 0; l <= *pos; ) {
>> +		m_def = enabled_monitors_next(m, m_def, &l);
>> +		if (!m_def)
>> +			break;
> 
> Is this check is inversed. enabled_monitors_start() will stop at first
> enabled monitor, then enabled_monitors_next() do loop to next. Check
> like the above, enabled_monitors_start() will loop to the last monitor.
> But I doubt myself I do not mention/see it. Sorry for these.
> 
> the check is:
> 
>   if (m_def)
>      break;
> 
> [...]


see kernel/trace/trace_events.c:s_start...

>> +static ssize_t
>> +enabled_monitors_write(struct file *filp, const char __user *user_buf,
>> +		      size_t count, loff_t *ppos)
>> +{
>> +	char buff[MAX_RV_MONITOR_NAME_SIZE + 2];
>> +	struct rv_monitor_def *mdef;
>> +	int retval = -EINVAL;
>> +	bool enable = true;
>> +	char *ptr = buff;
>> +	int len;
>> +
>> +	if (count < 1 || count > MAX_RV_MONITOR_NAME_SIZE + 2)
> 
> @count would not include '\0'. That the max val of @count is
> MAX_RV_MONITOR_NAME_SIZE+1. So the up bound check of @count is
> `count > MAX_RV_MONITOR_NAME_SIZE + 1`.

Fixed for v6...

-- Daniel