Commit b2fb01f4 authored Dec 20, 2017 by Cong Wang Committed by David S. Miller Dec 26, 2017

net_sched: fix a missing rcu barrier in mini_qdisc_pair_swap()



The rcu_barrier_bh() in mini_qdisc_pair_swap() is to wait for
flying RCU callback installed by a previous mini_qdisc_pair_swap(),
however we miss it on the tp_head==NULL path, which leads to that
the RCU callback still uses miniq_old->rcu after it is freed together
with qdisc in qdisc_graft(). So just add it on that path too.

Fixes: 46209401 ("net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath ")
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Tested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent c1a8d0a3

net/sched/sch_generic.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -1040,6 +1040,8 @@ void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,

		if (!tp_head) {
		RCU_INIT_POINTER(*miniqp->p_miniq, NULL);
		/* Wait for flying RCU callback before it is freed. */
		rcu_barrier_bh();
		return;
		}

		@@ -1055,7 +1057,7 @@ void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
		rcu_assign_pointer(*miniqp->p_miniq, miniq);

		if (miniq_old)
		/* This is counterpart of the rcu barrier above. We need to
		/* This is counterpart of the rcu barriers above. We need to
		* block potential new user of miniq_old until all readers
		* are not seeing it.
		*/

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