Re: [PATCH net] sctp: not allow to set asoc prsctp_enable by sockopt

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Thu, Nov 15, 2018 at 07:14:28PM +0800, Xin Long wrote:
> As rfc7496#section4.5 says about SCTP_PR_SUPPORTED:
> 
>    This socket option allows the enabling or disabling of the
>    negotiation of PR-SCTP support for future associations.  For existing
>    associations, it allows one to query whether or not PR-SCTP support
>    was negotiated on a particular association.
> 
> It means only sctp sock's prsctp_enable can be set.
> 
> Note that for the limitation of SCTP_{CURRENT|ALL}_ASSOC, we will
> add it when introducing SCTP_{FUTURE|CURRENT|ALL}_ASSOC for linux
> sctp in another patchset.
> 
> Fixes: 28aa4c26fce2 ("sctp: add SCTP_PR_SUPPORTED on sctp sockopt")
> Reported-by: Ying Xu <yinxu@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> ---
>  net/sctp/socket.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 739f3e5..e9b8232 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -3940,7 +3940,6 @@ static int sctp_setsockopt_pr_supported(struct sock *sk,
>  					unsigned int optlen)
>  {
>  	struct sctp_assoc_value params;
> -	struct sctp_association *asoc;
>  	int retval = -EINVAL;
>  
>  	if (optlen != sizeof(params))
> @@ -3951,16 +3950,10 @@ static int sctp_setsockopt_pr_supported(struct sock *sk,
>  		goto out;
>  	}
>  
> -	asoc = sctp_id2assoc(sk, params.assoc_id);
> -	if (asoc) {
> -		asoc->prsctp_enable = !!params.assoc_value;
> -	} else if (!params.assoc_id) {
> -		struct sctp_sock *sp = sctp_sk(sk);
> -
> -		sp->ep->prsctp_enable = !!params.assoc_value;
> -	} else {
> +	if (sctp_style(sk, UDP) && sctp_id2assoc(sk, params.assoc_id))

This would allow using a non-existent assoc id on UDP-style sockets to
set it at the socket, which is not expected. It should be more like:

+	if (sctp_style(sk, UDP) && params.assoc_id)

>  		goto out;
> -	}
> +
> +	sctp_sk(sk)->ep->prsctp_enable = !!params.assoc_value;
>  
>  	retval = 0;
>  
> -- 
> 2.1.0
>