Commit 95f4a45d authored Jan 13, 2014 by Hannes Frederic Sowa Committed by David S. Miller Jan 14, 2014

net: avoid reference counter overflows on fib_rules in multicast forwarding



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.

Fixes: f0ad0860 ("ipv4: ipmr: support multiple tables")
Fixes: d1db275d ("ipv6: ip6mr: support multiple tables")
Reported-by: Bob Falken <NetFestivalHaveFun@gmx.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7c4b5175

net/ipv4/ipmr.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -157,9 +157,12 @@ static struct mr_table ipmr_get_table(struct net net, u32 id)
		static int ipmr_fib_lookup(struct net net, struct flowi4 flp4,
		struct mr_table **mrt)
		{
		struct ipmr_result res;
		struct fib_lookup_arg arg = { .result = &res, };
		int err;
		struct ipmr_result res;
		struct fib_lookup_arg arg = {
		.result = &res,
		.flags = FIB_LOOKUP_NOREF,
		};

		err = fib_rules_lookup(net->ipv4.mr_rules_ops,
		flowi4_to_flowi(flp4), 0, &arg);

net/ipv6/ip6mr.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -141,9 +141,12 @@ static struct mr6_table ip6mr_get_table(struct net net, u32 id)
		static int ip6mr_fib_lookup(struct net net, struct flowi6 flp6,
		struct mr6_table **mrt)
		{
		struct ip6mr_result res;
		struct fib_lookup_arg arg = { .result = &res, };
		int err;
		struct ip6mr_result res;
		struct fib_lookup_arg arg = {
		.result = &res,
		.flags = FIB_LOOKUP_NOREF,
		};

		err = fib_rules_lookup(net->ipv6.mr6_rules_ops,
		flowi6_to_flowi(flp6), 0, &arg);

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