netdev - Re: [PATCHv2 net-next 1/4] sctp: define subscribe in sctp_sock as _

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Date:   Tue, 13 Nov 2018 12:15:21 -0500
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,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        davem@...emloft.net
Subject: Re: [PATCHv2 net-next 1/4] sctp: define subscribe in sctp_sock as
 __u16

On Tue, Nov 13, 2018 at 02:24:53PM +0800, Xin Long wrote:
>  
>  	/* Default Peer Address Parameters.  These defaults can
>  	 * be modified via SCTP_PEER_ADDR_PARAMS
> @@ -5267,14 +5274,24 @@ static int sctp_getsockopt_disable_fragments(struct sock *sk, int len,
>  static int sctp_getsockopt_events(struct sock *sk, int len, char __user *optval,
>  				  int __user *optlen)
>  {
> +	struct sctp_event_subscribe subscribe;
> +	__u8 *sn_type = (__u8 *)&subscribe;
> +	int i;
> +
>  	if (len == 0)
>  		return -EINVAL;
>  	if (len > sizeof(struct sctp_event_subscribe))
>  		len = sizeof(struct sctp_event_subscribe);
>  	if (put_user(len, optlen))
>  		return -EFAULT;
> -	if (copy_to_user(optval, &sctp_sk(sk)->subscribe, len))
> +
> +	for (i = 0; i <= len; i++)
> +		sn_type[i] = sctp_ulpevent_type_enabled(sctp_sk(sk)->subscribe,
> +							SCTP_SN_TYPE_BASE + i);
> +
This seems like an off by one error.  sctp_event_subscribe has N bytes in it (1
byte for each event), meaning that that events 0-(N-1) are subscribable.
Iterating this loop imples that you are going to check N events, overrunning the
sctp_event_subscribe struct.

Neil

>