netdev - Re: [PATCH net] tun: Fix use-after-free on XDP

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Date:   Fri, 13 Jul 2018 13:05:04 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH net] tun: Fix use-after-free on XDP_TX



On 2018年07月13日 12:24, Toshiaki Makita wrote:
> On XDP_TX we need to free up the frame only when tun_xdp_tx() returns a
> negative value. A positive value indicates that the packet is
> successfully enqueued to the ptr_ring, so freeing the page causes
> use-after-free.
>
> Fixes: 735fc4054b3a ("xdp: change ndo_xdp_xmit API to support bulking")
> Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> ---
>   drivers/net/tun.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index a192a01..f5727ba 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1688,7 +1688,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>   		case XDP_TX:
>   			get_page(alloc_frag->page);
>   			alloc_frag->offset += buflen;
> -			if (tun_xdp_tx(tun->dev, &xdp))
> +			if (tun_xdp_tx(tun->dev, &xdp) < 0)
>   				goto err_redirect;
>   			rcu_read_unlock();
>   			local_bh_enable();

Acked-by: Jason Wang <jasowang@...hat.com>