netdev - Re: [Patch net] can: initialize skbcnt in j1939_tp_tx_dat

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Date:   Thu, 8 Oct 2020 13:02:44 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        syzbot+3f3837e61a48d32b495f@...kaller.appspotmail.com,
        Robin van der Gracht <robin@...tonic.nl>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [Patch net] can: initialize skbcnt in j1939_tp_tx_dat_new()

On Thu, Oct 8, 2020 at 10:34 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed,  7 Oct 2020 23:18:21 -0700 Cong Wang wrote:
> > This fixes an uninit-value warning:
> > BUG: KMSAN: uninit-value in can_receive+0x26b/0x630 net/can/af_can.c:650
> >
> > Reported-and-tested-by: syzbot+3f3837e61a48d32b495f@...kaller.appspotmail.com
> > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
> > Cc: Robin van der Gracht <robin@...tonic.nl>
> > Cc: Oleksij Rempel <linux@...pel-privat.de>
> > Cc: Pengutronix Kernel Team <kernel@...gutronix.de>
> > Cc: Oliver Hartkopp <socketcan@...tkopp.net>
> > Cc: Marc Kleine-Budde <mkl@...gutronix.de>
> > Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> > ---
> >  net/can/j1939/transport.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
> > index 0cec4152f979..88cf1062e1e9 100644
> > --- a/net/can/j1939/transport.c
> > +++ b/net/can/j1939/transport.c
> > @@ -580,6 +580,7 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
> >       skb->dev = priv->ndev;
> >       can_skb_reserve(skb);
> >       can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
> > +     can_skb_prv(skb)->skbcnt = 0;
> >       /* reserve CAN header */
> >       skb_reserve(skb, offsetof(struct can_frame, data));
>
> Thanks! Looks like there is another can_skb_reserve(skb) on line 1489,
> is that one fine?

I don't know, I only attempt to address the syzbot report. To me,
it at least does not harm to fix that one too. I am fine either way.

Thanks.