linux-kernel - [PATCH AUTOSEL 5.18 44/68] net, neigh: Set lower cap for neigh_managed

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Date:   Tue,  7 Jun 2022 13:48:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Yuwei Wang <wangyuweihx@...il.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>, davem@...emloft.net,
        edumazet@...gle.com, pabeni@...hat.com, dsahern@...nel.org,
        roopa@...dia.com, yajun.deng@...ux.dev, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.18 44/68] net, neigh: Set lower cap for neigh_managed_work rearming

From: Daniel Borkmann <daniel@...earbox.net>

[ Upstream commit ed6cd6a17896561b9f51ab4c0d9bbb29e762b597 ]

Yuwei reported that plain reuse of DELAY_PROBE_TIME to rearm work queue
in neigh_managed_work is problematic if user explicitly configures the
DELAY_PROBE_TIME to 0 for a neighbor table. Such misconfig can then hog
CPU to 100% processing the system work queue. Instead, set lower interval
bound to HZ which is totally sufficient. Yuwei is additionally looking
into making the interval separately configurable from DELAY_PROBE_TIME.

Reported-by: Yuwei Wang <wangyuweihx@...il.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Link: https://lore.kernel.org/netdev/797c3c53-ce1b-9f60-e253-cda615788f4a@iogearbox.net
Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>
Link: https://lore.kernel.org/r/3b8c5aa906c52c3a8c995d1b2e8ccf650ea7c716.1653432794.git.daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/neighbour.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index f64ebd050f6c..fd69133dc7c5 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1579,7 +1579,7 @@ static void neigh_managed_work(struct work_struct *work)
 	list_for_each_entry(neigh, &tbl->managed_list, managed_list)
 		neigh_event_send_probe(neigh, NULL, false);
 	queue_delayed_work(system_power_efficient_wq, &tbl->managed_work,
-			   NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME));
+			   max(NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME), HZ));
 	write_unlock_bh(&tbl->lock);
 }
 
-- 
2.35.1