[PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

[Alexander Mikhalitsyn]

Cc: Julian Anastasov <ja@xxxxxx>
Cc: Simon Horman <horms@xxxxxxxxxxxx>
Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>
Cc: Florian Westphal <fw@xxxxxxxxx>
Suggested-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 143a341bbc0a..daa62b8b2dd1 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -94,6 +94,7 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 {
 	struct sysinfo i;
 	int availmem;
+	int amemthresh;
 	int nomem;
 	int to_change = -1;
 
@@ -105,7 +106,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	/* si_swapinfo(&i); */
 	/* availmem = availmem - (i.totalswap - i.freeswap); */
 
-	nomem = (availmem < ipvs->sysctl_amemthresh);
+	amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0);
+	nomem = (availmem < amemthresh);
 
 	local_bh_disable();
 
@@ -146,8 +148,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	case 1:
 		if (nomem) {
 			ipvs->drop_rate = ipvs->drop_counter
-				= ipvs->sysctl_amemthresh /
-				(ipvs->sysctl_amemthresh-availmem);
+				= amemthresh /
+				(amemthresh-availmem);
 			ipvs->sysctl_drop_packet = 2;
 		} else {
 			ipvs->drop_rate = 0;
@@ -156,8 +158,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	case 2:
 		if (nomem) {
 			ipvs->drop_rate = ipvs->drop_counter
-				= ipvs->sysctl_amemthresh /
-				(ipvs->sysctl_amemthresh-availmem);
+				= amemthresh /
+				(amemthresh-availmem);
 		} else {
 			ipvs->drop_rate = 0;
 			ipvs->sysctl_drop_packet = 1;
-- 
2.34.1