Re: [PATCH net-next] ipvs: properly dereference pe in ip_vs_add_service

[Julian Anastasov <ja@xxxxxx>]

        Hello,

On Wed, 26 Jun 2024, Chen Hanxiao wrote:

> Use rcu_dereference_protected to resolve sparse warning:
> 
>   net/netfilter/ipvs/ip_vs_ctl.c:1471:27: warning: dereference of noderef 
> expression
> 
> Fixes: 39b972231536 ("ipvs: handle connections started by real-servers")
> Signed-off-by: Chen Hanxiao <chenhx.fnst@xxxxxxxxxxx>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index b6d0dcf3a5c3..925e2143ba15 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -1369,7 +1369,7 @@ ip_vs_add_service(struct netns_ipvs *ipvs, struct 
> ip_vs_service_user_kern *u,
>  {
>       int ret = 0;
>       struct ip_vs_scheduler *sched = NULL;
> -     struct ip_vs_pe *pe = NULL;
> +     struct ip_vs_pe *pe = NULL, *tmp_pe = NULL;

        NULL init is not needed

>       struct ip_vs_service *svc = NULL;
>       int ret_hooks = -1;
>  
> @@ -1468,7 +1468,8 @@ ip_vs_add_service(struct netns_ipvs *ipvs, struct 
> ip_vs_service_user_kern *u,
>               atomic_inc(&ipvs->ftpsvc_counter);
>       else if (svc->port == 0)
>               atomic_inc(&ipvs->nullsvc_counter);
> -     if (svc->pe && svc->pe->conn_out)
> +     tmp_pe = rcu_dereference_protected(svc->pe, 1);
> +     if (tmp_pe && tmp_pe->conn_out)
>               atomic_inc(&ipvs->conn_out_counter);

        Alternative option would be to use 'pe' above and to move
the RCU_INIT_POINTER and pe = NULL with their comment here.
It is up to you to decide which option is better...

Regards

--
Julian Anastasov <ja@xxxxxx>