netdev - Re: [PATCH net-next] tun: use sk_fullsock() before reading sk->sk

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Date:	Sun, 11 Oct 2015 09:06:03 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] tun: use sk_fullsock() before reading
 sk->sk_tsflags

On Fri, Oct 09, 2015 at 03:42:21PM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> timewait or request sockets are small and do not contain sk->sk_tsflags
> 
> Without this fix, we might read garbage, and crash later in
> 
> __skb_complete_tx_timestamp()
>  -> sock_queue_err_skb()
> 
> (These pseudo sockets do not have an error queue either)
> 
> Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>


Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  Note this bug also exists on net tree for timewait sockets but only
>  in exceptional conditions (routing glitches and IP early demux)
> 
>  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 976aa9704297..b1878faea397 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -858,7 +858,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
>  	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
>  		goto drop;
>  
> -	if (skb->sk) {
> +	if (skb->sk && sk_fullsock(skb->sk)) {
>  		sock_tx_timestamp(skb->sk, &skb_shinfo(skb)->tx_flags);
>  		sw_tx_timestamp(skb);
>  	}
> 
> 
> --
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