Subject: Re: [PATCH] net: Fix sk reference counting in ip_push_pending_frames and ip6_push_pending_frames

From: Eric Dumazet <[email-masked]>
Date: Sat, 11 Jul 2009 21:39:39 +0200

John Dykstra a écrit :
> Commit 2b85a34e911bf483c27cfdd124aeb1605145dc80 "net: No more expensive
> sock_hold()/sock_put() on each tx" used sk_wmem_alloc rather than the struct sock reference
> count to track in-flight transmit-path packets.  However, it missed the __sock_put() calls
> in ip_push_pending_frames() and ip6_push_pending_frames().  This results in too-small
> reference counts when UDP or RAW sockets are used to send more than one MTU of data.  This 
> in turn could lead to struct sock being freed and reused while it is still part of an
> active socket.
> 
> A wide variety of socket symptoms may be fixed by this patch.  It also fixes one cause 
> of WARN_ON's in sk_del_node_init() and sk_nulls_del_node_init_rcu().
> 
> Signed-off-by: John Dykstra <[email-masked]>

Nice, but are you aware same patch was already posted, and is waiting for David
approval ?

http://patchwork.ozlabs.org/patch/29618/

> ---
>  net/ipv4/ip_output.c  |    1 -
>  net/ipv6/ip6_output.c |    1 -
>  2 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 2470262..7d08210 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -1243,7 +1243,6 @@ int ip_push_pending_frames(struct sock *sk)
>  		skb->len += tmp_skb->len;
>  		skb->data_len += tmp_skb->len;
>  		skb->truesize += tmp_skb->truesize;
> -		__sock_put(tmp_skb->sk);
>  		tmp_skb->destructor = NULL;
>  		tmp_skb->sk = NULL;
>  	}
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 7c76e3d..87f8419 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1484,7 +1484,6 @@ int ip6_push_pending_frames(struct sock *sk)
>  		skb->len += tmp_skb->len;
>  		skb->data_len += tmp_skb->len;
>  		skb->truesize += tmp_skb->truesize;
> -		__sock_put(tmp_skb->sk);
>  		tmp_skb->destructor = NULL;
>  		tmp_skb->sk = NULL;
>  	}