netdev - Re: [PATCH RFC net-next 3/3] net/core/sock.c: sk_clone_lock() should only do get_net() if the parent is not a kernel socket

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Date:	Thu, 30 Jul 2015 15:06:47 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	netdev@...r.kernel.org, cwang@...pensource.com,
	ajaykumar.hotchandani@...cle.com,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH RFC net-next 3/3] net/core/sock.c: sk_clone_lock()
 should only do get_net() if the parent is not a kernel socket

On Thu, 2015-07-30 at 04:55 -0400, Sowmini Varadhan wrote:
> The newsk returned by sk_clone_lock should hold a get_net()
> reference if, and only if, the parent is not a kernel socket
> (making this similar to sk_alloc()).
> 
> E.g,. for the SYN_RECV call path, tcp_v4_syn_recv_sock->..inet_csk_clone_lock
> sets up the syn_recv newsk from sk_clone_lock. When the parent (listen)
> socket is a kernel socket (defined in sk_alloc() as having
> sk_net_refcnt == 0), then the newsk should also have a 0 sk_net_refcnt
> and should not hold a get_net() reference.
> 
> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
> ---
>  net/core/sock.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 08f16db..371d1b7 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1497,7 +1497,8 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
>  		sock_copy(newsk, sk);
>  
>  		/* SANITY */
> -		get_net(sock_net(newsk));
> +		if (likely(newsk->sk_net_refcnt))
> +			get_net(sock_net(newsk));
>  		sk_node_init(&newsk->sk_node);
>  		sock_lock_init(newsk);
>  		bh_lock_sock(newsk);

CC Eric Biederman 

It looks this should be submitted for 'net' tree, not 'net-next'

Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")

Acked-by: Eric Dumazet <edumazet@...gle.com>




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