netdev - Re: [PATCH v2 bpf-next] libbpf: fix GCC8 warning for strncpy

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Message-ID: <CAJ8uoz37Ukj1qaZre1-=Rm3GZkkxGW8zxQ85fg5YLHaMWXNp3g@mail.gmail.com>
Date:   Tue, 2 Jul 2019 18:38:32 +0200
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Y Song <ys114321@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        bpf <bpf@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>
Subject: Re: [PATCH v2 bpf-next] libbpf: fix GCC8 warning for strncpy

On Tue, Jul 2, 2019 at 6:11 PM Y Song <ys114321@...il.com> wrote:
>
> On Tue, Jul 2, 2019 at 8:17 AM Andrii Nakryiko <andriin@...com> wrote:
> >
> > GCC8 started emitting warning about using strncpy with number of bytes
> > exactly equal destination size, which is generally unsafe, as can lead
> > to non-zero terminated string being copied. Use IFNAMSIZ - 1 as number
> > of bytes to ensure name is always zero-terminated.
> >
> > Cc: Magnus Karlsson <magnus.karlsson@...el.com>
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
>
> Acked-by: Yonghong Song <yhs@...com>

Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>

>
> > ---
> >  tools/lib/bpf/xsk.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> > index bf15a80a37c2..b33740221b7e 100644
> > --- a/tools/lib/bpf/xsk.c
> > +++ b/tools/lib/bpf/xsk.c
> > @@ -327,7 +327,8 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
> >
> >         channels.cmd = ETHTOOL_GCHANNELS;
> >         ifr.ifr_data = (void *)&channels;
> > -       strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ);
> > +       strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
> > +       ifr.ifr_name[IFNAMSIZ - 1] = '\0';
> >         err = ioctl(fd, SIOCETHTOOL, &ifr);
> >         if (err && errno != EOPNOTSUPP) {
> >                 ret = -errno;
> > --
> > 2.17.1
> >