linux-kernel - Re: [PATCH] hwmon: (applesmc) Fix checkpatch errors

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Date:	Wed, 10 Nov 2010 20:56:20 +0100
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Guenter Roeck <guenter.roeck@...csson.com>
CC:	Jean Delvare <khali@...ux-fr.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hwmon: (applesmc) Fix checkpatch errors

>>> @@ -977,7 +975,11 @@ static ssize_t applesmc_key_at_index_show

>>>  static ssize_t applesmc_key_at_index_store(struct device *dev,
>>>  	struct device_attribute *attr, const char *sysfsbuf, size_t count)
>>>  {
>>> -	key_at_index = simple_strtoul(sysfsbuf, NULL, 10);
>>> +	unsigned long newkey;
>>> +
>>> +	if (strict_strtoul(sysfsbuf, 10, &newkey) < 0)
>>> +		return -EINVAL;
>>> +	key_at_index = newkey;
>>
>>
>> Crash alert - key_at_index is not range checked, and the remake uses this value
>> as an array index...
>>
> Good that I made this change ;). I'll add the check and re-send.


Indeed! The downside of remakes... sorry about that. :-)

I guess the change should go into patch 4 already? There is also the option to
put the bounds check in applesmc_get_entry_by_index, but I like the simplicity
of "|| newkey >= smcreg.key_count".

> This points to another problem, though. You allocate key_count entries,
> ie cache[0]..cache[key_count-1]. Yet, the key searches are from 0..key_count,
> ie span key_count+1 entries. Is that another problem ?

>

> Seems to me you would either have to allocate key_count+1 entries, or terminate
> the search at key_count - 1. Not sure which one would be correct. Let me know,
> and I'll update the affected patch(es).


If you are referring to the lower and upper bound functions, those use the
one-past-the-last-element convention, so it is actually still 0..key_count - 1.
I stayed very close to the stl reference implementation, which relies on the
fact that when begin != end, (begin + (end - begin) / 2) < end.

Cheers,
Henrik
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