netdev - Re: [PATCH] netfilter: fix buffer null termination

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Message-ID: <20160614150802.GA1029@salvia>
Date:	Tue, 14 Jun 2016 17:08:02 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Kishan Sandeep <sandeepkishan108@...il.com>
Cc:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] netfilter: fix buffer null termination

Cc'ing netfilter-devel.

On Tue, Jun 14, 2016 at 07:39:27PM +0530, Kishan Sandeep wrote:
> + netdev
> 
> On Sat, Jun 11, 2016 at 10:18 AM, Kishan Sandeep
> <sandeepkishan108@...il.com> wrote:
> > strncpy generally perferable fo non-terminated
> > fixed-width strings. For NULL termination strlcpy
> > is preferrable.
> >
> > Signed-off-by: Kishan Sandeep <sandeepkishan108@...il.com>
> > ---
> >  net/netfilter/xt_repldata.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/netfilter/xt_repldata.h b/net/netfilter/xt_repldata.h
> > index 8fd3241..a460211 100644
> > --- a/net/netfilter/xt_repldata.h
> > +++ b/net/netfilter/xt_repldata.h
> > @@ -28,7 +28,7 @@
> >         if (tbl == NULL) \
> >                 return NULL; \
> >         term = (struct type##_error *)&(((char *)tbl)[term_offset]); \
> > -       strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \
> > +       strlcpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \

I don't think this is actually fixing anything. Tables in x_tables
have a known and fixed name that is defined from the kernel side, that
is always smaller that the buffer we have there. So are you observing
any real problem from there?

Thanks.