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

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Date:   Thu, 8 Oct 2020 10:34:10 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     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 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?

Marc - should I take this directly into net, in case there is a last
minute PR to Linus for 5.9?