Re: [PATCH 4.2.y-ckt 225/273] tipc: fix connection abort during subscription cancel

[Kamal Mostafa <kamal@canonical.com>]

On Mon, 2016-03-07 at 14:50 -0800, Kamal Mostafa wrote:
> 4.2.8-ckt5 -stable review patch.  If anyone has any objections,
> please let me know.

This patch will be deferred to the next 4.2-stable release (4.2.8-ckt6) 
so that it lands along with

4de13d7e tipc: fix nullptr crash during subscription cancel

... which has not yet appeared in a mainline -rc.

 -Kamal


> ---8<------------------------------------------------------------
> 
> From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com
> >
> 
> [ Upstream commit 4d5cfcba2f6ec494d8810b9e3c0a7b06255c8067 ]
> 
> In 'commit 7fe8097cef5f ("tipc: fix nullpointer bug when subscribing
> to events")', we terminate the connection if the subscription
> creation fails.
> In the same commit, the subscription creation result was based on
> the value of the subscription pointer (set in the function) instead
> of the return code.
> 
> Unfortunately, the same function tipc_subscrp_create() handles
> subscription cancel request. For a subscription cancellation request,
> the subscription pointer cannot be set. Thus if a subscriber has
> several subscriptions and cancels any of them, the connection is
> terminated.
> 
> In this commit, we terminate the connection based on the return value
> of tipc_subscrp_create().
> Fixes: commit 7fe8097cef5f ("tipc: fix nullpointer bug when
> subscribing to events")
> 
> Reviewed-by:  Jon Maloy <jon.maloy@ericsson.com>
> Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@eri
> csson.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Kamal Mostafa <kamal@canonical.com>
> ---
>  net/tipc/subscr.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
> index 350cca3..69ee2ee 100644
> --- a/net/tipc/subscr.c
> +++ b/net/tipc/subscr.c
> @@ -289,15 +289,14 @@ static void tipc_subscrb_rcv_cb(struct net
> *net, int conid,
>  				struct sockaddr_tipc *addr, void
> *usr_data,
>  				void *buf, size_t len)
>  {
> -	struct tipc_subscriber *subscriber = usr_data;
> +	struct tipc_subscriber *subscrb = usr_data;
>  	struct tipc_subscription *sub = NULL;
>  	struct tipc_net *tn = net_generic(net, tipc_net_id);
>  
> -	tipc_subscrp_create(net, (struct tipc_subscr *)buf,
> subscriber, &sub);
> -	if (sub)
> -		tipc_nametbl_subscribe(sub);
> -	else
> -		tipc_conn_terminate(tn->topsrv, subscriber->conid);
> +	if (tipc_subscrp_create(net, (struct tipc_subscr *)buf,
> subscrb, &sub))
> +		return tipc_conn_terminate(tn->topsrv, subscrb-
> >conid);
> +
> +	tipc_nametbl_subscribe(sub);
>  }
>  
>  /* Handle one request to establish a new subscriber */