netdev - Re: [PATCH] inet: add RCU protection to inet->opt

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Date:	Thu, 28 Apr 2011 22:49:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	herbert@...dor.apana.org.au, netdev@...r.kernel.org
Subject: Re: [PATCH] inet: add RCU protection to inet->opt

Le jeudi 28 avril 2011 à 13:20 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 21 Apr 2011 21:45:37 +0200
> 
> > [PATCH] inet: add RCU protection to inet->opt
> 
> Applied, although I had to add the following build fix to the
> final commit:
> 
> diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
> index cc67367..962a607 100644
> --- a/net/l2tp/l2tp_ip.c
> +++ b/net/l2tp/l2tp_ip.c
> @@ -416,7 +416,6 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
>  	int rc;
>  	struct l2tp_ip_sock *lsa = l2tp_ip_sk(sk);
>  	struct inet_sock *inet = inet_sk(sk);
> -	struct ip_options *opt = inet->opt;
>  	struct rtable *rt = NULL;
>  	int connected = 0;
>  	__be32 daddr;
> @@ -471,9 +470,14 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
>  		rt = (struct rtable *) __sk_dst_check(sk, 0);
>  
>  	if (rt == NULL) {
> +		struct ip_options_rcu *inet_opt;
> +
> +		inet_opt = rcu_dereference_protected(inet->inet_opt,
> +						     sock_owned_by_user(sk));
> +
>  		/* Use correct destination address if we have options. */
> -		if (opt && opt->srr)
> -			daddr = opt->faddr;
> +		if (inet_opt && inet_opt->opt.srr)
> +			daddr = inet_opt->opt.faddr;
>  
>  		/* If this fails, retransmit mechanism of transport layer will
>  		 * keep trying until route appears or the connection times

Gah... I wonder how I missed it.

Are you sure socket is locked at this point ? ( by a priori call to
lock_sock())

Thanks !


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