[Devel] [PATCH rh7] net: avoid reference counter overflows on fib_rules in multicast forwarding

[Andrey Ryabinin]

On 11/23/2015 07:08 PM, Stanislav Kinsburskiy wrote:
> From: Hannes Frederic Sowa <hannes at stressinduktion.org>
> 
> Bob Falken reported that after 4G packets, multicast forwarding stopped
> working. This was because of a rule reference counter overflow which
> freed the rule as soon as the overflow happend.
> 
> This patch solves this by adding the FIB_LOOKUP_NOREF flag to
> fib_rules_lookup calls. This is safe even from non-rcu locked sections
> as in this case the flag only implies not taking a reference to the rule,
> which we don't need at all.
> 
> Rules only hold references to the namespace, which are guaranteed to be
> available during the call of the non-rcu protected function reg_vif_xmit
> because of the interface reference which itself holds a reference to
> the net namespace.
> 
> Backport: https://jira.sw.ru/browse/PSBM-41453
> 
> Fixes: f0ad0860d01e47 ("ipv4: ipmr: support multiple tables")
> Fixes: d1db275dd3f6e4 ("ipv6: ip6mr: support multiple tables")
> Reported-by: Bob Falken <NetFestivalHaveFun at gmx.com>
> Cc: Patrick McHardy <kaber at trash.net>
> Cc: Thomas Graf <tgraf at suug.ch>
> Cc: Julian Anastasov <ja at ssi.bg>
> Cc: Eric Dumazet <eric.dumazet at gmail.com>
> Signed-off-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
> Acked-by: Eric Dumazet <edumazet at google.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at odin.com>
> ---
>  net/ipv4/ipmr.c  |    7 +++++--
>  net/ipv6/ip6mr.c |    7 +++++--
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 

What about dn_fib_lookup()? Do we need a similar patch  for it?
Anyway, this patch LGTM:
	Reviewed-by: Andrey Ryabinin <aryabinin at virtuozzo.com>