netdev - Re: [PATCH] ipvs: explicitly forbid ipv6 service/dest creation if ipv6 mod is disabled

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Date:   Sat, 22 Apr 2017 14:16:34 +0300 (EEST)
From:   Julian Anastasov <ja@....bg>
To:     Paolo Abeni <pabeni@...hat.com>
cc:     netfilter-devel@...r.kernel.org, lvs-devel@...r.kernel.org,
        Wensong Zhang <wensong@...ux-vs.org>,
        Simon Horman <horms@...ge.net.au>, netdev@...r.kernel.org
Subject: Re: [PATCH] ipvs: explicitly forbid ipv6 service/dest creation if
 ipv6 mod is disabled


	Hello,

On Thu, 20 Apr 2017, Paolo Abeni wrote:

> When creating a new ipvs service, ipv6 addresses are always accepted
> if CONFIG_IP_VS_IPV6 is enabled. On dest creation the address family
> is not explicitly checked.
> 
> This allows the user-space to configure ipvs services even if the
> system is booted with ipv6.disable=1. On specific configuration, ipvs
> can try to call ipv6 routing code at setup time, causing the kernel to
> oops due to fib6_rules_ops being NULL.
> 
> This change addresses the issue adding a check for the ipv6
> module being enabled while validating ipv6 service operations and
> adding the same validation for dest operations.
> 
> According to git history, this issue is apparently present since
> the introduction of ipv6 support, and the oops can be triggered
> since commit 09571c7ae30865ad ("IPVS: Add function to determine
> if IPv6 address is local")
> 
> Fixes: 09571c7ae30865ad ("IPVS: Add function to determine if IPv6 address is local")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

	Looks good to me but I see two places that can benefit
from such check:

- in ip_vs_genl_new_daemon() if we do not want to create IPv6 sockets
for the sync protocol in make_send_sock() and make_receive_sock().
Not sure if this can lead to crashes.

- in ip_vs_proc_sync_conn() if we do not want backup server to accept 
IPv6 conns because they may be created even when dests are missing.
We may use retc = 10 there. Not fatal but may eat memory for
conns that will not be used.

Regards

--
Julian Anastasov <ja@....bg>