Re: [PATCH] staging: rtl8192e: prefer strscpy over strncpy

[Dan Carpenter]

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