net, neigh: Set lower cap for neigh_managed_work rearming

borkmann · kuba-moo · commit ed6cd6a17896 · 2022-05-25T22:00:48.000-07:00
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@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/netdev/797c3c53-ce1b-9f60-e253-cda615788f4a@iogearbox.net Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Link: https://lore.kernel.org/r/3b8c5aa906c52c3a8c995d1b2e8ccf650ea7c716.1653432794.git.daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git 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);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1579,7 +1579,7 @@ static void neigh_managed_work(struct work_struct *work)`
`1579`	`1579`	`list_for_each_entry(neigh, &tbl->managed_list, managed_list)`
`1580`	`1580`	`neigh_event_send_probe(neigh, NULL, false);`
`1581`	`1581`	`queue_delayed_work(system_power_efficient_wq, &tbl->managed_work,`
`1582`		`- NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME));`
	`1582`	`+ max(NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME), HZ));`
`1583`	`1583`	`write_unlock_bh(&tbl->lock);`
`1584`	`1584`	`}`
`1585`	`1585`