netdev - Re: [PATCH net] sctp: ensure ep is not destroyed before doing the dump

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Message-ID: <20170619112833.GA6487@hmswarspite.think-freely.org>
Date:   Mon, 19 Jun 2017 07:28:33 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] sctp: ensure ep is not destroyed before doing the
 dump

On Sat, Jun 17, 2017 at 04:10:27PM +0800, Xin Long wrote:
> Now before dumping a sock in sctp_diag, it only holds the sock while
> the ep may be already destroyed. It can cause a use-after-free panic
> when accessing ep->asocs.
> 
> This patch is to set sctp_sk(sk)->ep NULL in sctp_endpoint_destroy,
> and check if this ep is already destroyed before dumping this ep.
> 
> Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/endpointola.c | 1 +
>  net/sctp/sctp_diag.c   | 5 +++--
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c
> index 8c58923..3dcd0ec 100644
> --- a/net/sctp/endpointola.c
> +++ b/net/sctp/endpointola.c
> @@ -275,6 +275,7 @@ static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
>  		if (sctp_sk(sk)->bind_hash)
>  			sctp_put_port(sk);
>  
> +		sctp_sk(sk)->ep = NULL;
>  		sock_put(sk);
>  	}
>  
> diff --git a/net/sctp/sctp_diag.c b/net/sctp/sctp_diag.c
> index 048954e..9a64721 100644
> --- a/net/sctp/sctp_diag.c
> +++ b/net/sctp/sctp_diag.c
> @@ -278,7 +278,6 @@ static int sctp_tsp_dump_one(struct sctp_transport *tsp, void *p)
>  
>  static int sctp_sock_dump(struct sock *sk, void *p)
>  {
> -	struct sctp_endpoint *ep = sctp_sk(sk)->ep;
>  	struct sctp_comm_param *commp = p;
>  	struct sk_buff *skb = commp->skb;
>  	struct netlink_callback *cb = commp->cb;
> @@ -287,7 +286,9 @@ static int sctp_sock_dump(struct sock *sk, void *p)
>  	int err = 0;
>  
>  	lock_sock(sk);
> -	list_for_each_entry(assoc, &ep->asocs, asocs) {
> +	if (!sctp_sk(sk)->ep)
> +		goto release;
> +	list_for_each_entry(assoc, &sctp_sk(sk)->ep->asocs, asocs) {
>  		if (cb->args[4] < cb->args[1])
>  			goto next;
>  
> -- 
> 2.1.0
> 
> 
Acked-by: Neil Horman <nhorman@...drver.com>