netdev - RE: tainted warnings with tcp splicing in 3.7.1

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Date:	Thu, 10 Jan 2013 19:27:26 +0100
From:	Lukas Tribus <luky-37@...mail.com>
To:	<eric.dumazet@...il.com>
CC:	<netdev@...r.kernel.org>
Subject: RE: tainted warnings with tcp splicing in 3.7.1


Hi Eric,

this is probably a dumb question ... but since the fix is in net/ipv4/tcp.c I was asking myself if this can affect IPv6 as well?



Thanks,

Lukas


> [PATCH] tcp: fix splice() and tcp collapsing interaction
> 
> Under unusual circumstances, TCP collapse can split a big GRO TCP packet
> while its being used in a splice(socket->pipe) operation.
> 
> skb_splice_bits() releases the socket lock before calling
> splice_to_pipe().
> 
> [ 1081.353685] WARNING: at net/ipv4/tcp.c:1330 tcp_cleanup_rbuf+0x4d/0xfc()
> [ 1081.371956] Hardware name: System x3690 X5 -[7148Z68]-
> [ 1081.391820] cleanup rbuf bug: copied AD3BCF1 seq AD370AF rcvnxt AD3CF13
> 
> To fix this problem, we must eat skbs in tcp_recv_skb().
> 
> Remove the inline keyword from tcp_recv_skb() definition since
> it has three call sites.
> 
> Reported-by: Christian Becker <c.becker@...viangames.com>
> Cc: Willy Tarreau <w@....eu>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/ipv4/tcp.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1ca2536..1f901be 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1428,12 +1428,12 @@ static void tcp_service_net_dma(struct sock *sk, bool wait)
>  }
>  #endif
>  
> -static inline struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
> +static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
>  {
>  	struct sk_buff *skb;
>  	u32 offset;
>  
> -	skb_queue_walk(&sk->sk_receive_queue, skb) {
> +	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
>  		offset = seq - TCP_SKB_CB(skb)->seq;
>  		if (tcp_hdr(skb)->syn)
>  			offset--;
> @@ -1441,6 +1441,11 @@ static inline struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
>  			*off = offset;
>  			return skb;
>  		}
> +		/* This looks weird, but this can happen if TCP collapsing
> +		 * splitted a fat GRO packet, while we released socket lock
> +		 * in skb_splice_bits()
> +		 */
> +		sk_eat_skb(sk, skb, false);
>  	}
>  	return NULL;
>  }
> @@ -1520,8 +1525,10 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
>  	tcp_rcv_space_adjust(sk);
>  
>  	/* Clean up data we have read: This will do ACK frames. */
> -	if (copied > 0)
> +	if (copied > 0) {
> +		tcp_recv_skb(sk, seq, &offset);
>  		tcp_cleanup_rbuf(sk, copied);
> +	}
>  	return copied;
>  }
>  EXPORT_SYMBOL(tcp_read_sock);
> 
 		 	   		  --
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