linux-kernel - Re: [PATCH] staging: rtl8192e: prefer strscpy over strncpy

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Message-ID: <69226eca-d345-f6fa-59fe-3c55674cc534@gmail.com>
Date:   Fri, 25 Aug 2023 07:13:42 +0200
From:   Michael Straube <straube.linux@...il.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>, philipp.g.hortmann@...il.com,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8192e: prefer strscpy over strncpy

On 8/10/23 07:01, Dan Carpenter wrote:
> On Wed, Aug 09, 2023 at 08:02:05PM +0200, Michael Straube wrote:
>> On 8/9/23 14:21, Greg KH wrote:
>>> On Sat, Aug 05, 2023 at 09:51:14AM +0200, Michael Straube wrote:
>>>> Replace strncpy with strscpy in two places where the destination buffer
>>>> should be NUL-terminated. Found by checkpatch.
>>>>
>>>> WARNING: Prefer strscpy, strscpy_pad, or __nonstring over strncpy - see: https://github.com/KSPP/linux/issues/90
>>>
>>> If a global search/replace could be done, it would have happend a long
>>> time ago.
>>>
>>> How was this tested?  The functions work differently, are you sure there
>>> is no change in functionality here?
>>>
>>
>> It was only compile tested. To me it looked as it does not change
>> functionality, but looking a bit deeper at it I'm not sure anymore.
>> So, we should leave it as is.
> 
> So there are three main differences between strncpy() and strcpy().
> 
> 1) The return.
> 2) strncpy() will always write net->hidden_ssid_len bytes.  If the
>     string to copy is smaller than net->hidden_ssid_len bytes it will
>     fill the rest with zeroes.  This can be important for preventing
>     information leaks.
> 3) strscpy() will always add a NUL terminator where strncpy() just
>     truncates a too long string without adding a terminator.
> 
> We want #3.  We don't care about #1.  The only thing to check is #2.
> 
> regards,
> dan carpenter
> 

Thank you Dan,

so in this case we should/could replace strncpy with strscpy_pad,
correct?

regards,
Michael