Re: [PATCH] net: ipconfig: replace strncpy with strscpy_pad

[Nelson, Shannon]

On 4/10/2025 12:59 PM, Pranav Tyagi wrote:
> On Wed, Apr 9, 2025 at 3:14 AM Nelson, Shannon <shannon.nelson@xxxxxxx> wrote:
> > On 4/8/2025 11:57 AM, Pranav Tyagi wrote:
> > > Replace the deprecated strncpy() function with strscpy_pad() as the
> > > destination buffer is NUL-terminated and requires
> > > trailing NUL-padding
> > >
> > > Signed-off-by: Pranav Tyagi <pranav.tyagi03@xxxxxxxxx>
> >
> > There should be a Fixes tag here, and usually we put the 'net' tree
> > indicator inside the tag, like this: [PATCH net]
> >
> >
> > > ---
> > >    net/ipv4/ipconfig.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
> > > index c56b6fe6f0d7..7c238d19328f 100644
> > > --- a/net/ipv4/ipconfig.c
> > > +++ b/net/ipv4/ipconfig.c
> > > @@ -1690,7 +1690,7 @@ static int __init ic_proto_name(char *name)
> > >                           *v = 0;
> > >                           if (kstrtou8(client_id, 0, dhcp_client_identifier))
> > >                                   pr_debug("DHCP: Invalid client identifier type\n");
> > > -                       strncpy(dhcp_client_identifier + 1, v + 1, 251);
> > > +                       strscpy_pad(dhcp_client_identifier + 1, v + 1, 251);
> >
> > The strncpy() action, as well as the memcpy() into
> > dhcp_client_identifier elsewhere, are not padding to the end, so I think
> > this only needs to be null-terminated, not fully padded.  If full
> > padding is needed, please let us know why.
> >
> > sln
> >
> > >                           *v = ',';
> > >                   }
> > >                   return 1;
> > > --
> > > 2.49.0
>
> My initial assumption was on the fact that dhcp_client_identifier
> is directly used in DHCP packet construction
> and may be parsed byte-wise. But on going through the code again
> I see that it does not require to be fully padded.
> Would strscpy() suffice? as it ensures null-termination and
> does not fully pad the buffer.

Yes, strscpy() should work.
sln


> Regards
> Pranav Tyagi