linux-kernel - Re: [PATCH] atmel: using strlcpy() to avoid possible buffer overflows

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Date:   Sat, 30 Jun 2018 14:30:34 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     <simon@...kelleys.org.uk>, Kalle Valo <kvalo@...eaurora.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "open list:TI WILINK WIRELES..." <linux-wireless@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] atmel: using strlcpy() to avoid possible buffer overflows


On 2018/6/30 5:51, Andy Shevchenko wrote:
> On Sat, Jun 30, 2018 at 12:47 AM, Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
>> On Fri, Jun 29, 2018 at 5:51 AM, YueHaibing <yuehaibing@...wei.com> wrote:
>>> 'firmware' is a module param which may been longer than firmware_id,
>>> so using strlcpy() to guard against overflows
>>
>> strncat() is against overflow, this does a bit more.
>>
>>>         priv->firmware_id[0] = '\0';
>> ...
>>>         if (firmware) /* module parameter */
>>> -               strcpy(priv->firmware_id, firmware);
>>> +               strlcpy(priv->firmware_id, firmware, sizeof(priv->firmware_id));
>>
>> In either case the above '\0' is not needed.
>> But it looks like the intention was to use strncat() / strlcat().
> 
> Ah, this is under condition, yes. If no parameter supplied, this needs
> to be clean, but
> priv is allocated with zeroed memory
> https://elixir.bootlin.com/linux/latest/source/net/core/dev.c#L8369

so just remove this line:
	 priv->firmware_id[0] = '\0';

and using strlcpy while 'firmware' NOT null is enough.

Will send v2.

>