[PATCH nf v2 1/1] ipvs: bound LBLCR and LBLC cache growth

ip_vs_lblcr_new() and ip_vs_lblc_new() create cache entries for
every previously unseen destination address. The table max_size only
tells the periodic collector to reclaim entries after the cache has
already exceeded the limit. It does not reclaim entries that the
attacker continues to use.

Reject new cache entries once either table grows beyond max_size. The
existing scheduler fallback continues to use the selected destination
when cache creation fails, so new traffic stays serviceable without
growing the tables further.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: [email protected]
Reported-by: Vega <[email protected]>
Suggested-by: Julian Anastasov <[email protected]>
Signed-off-by: Zhiling Zou <[email protected]>
---
changes in v2:
- Change the LBLCR limit check from >= max_size to > max_size.
- Apply the same cache growth bound to LBLC.
- Add Suggested-by: Julian Anastasov <[email protected]>.
- v1 Link: https://lore.kernel.org/all/62790a9f94ac5318f107a1811cff5a1f2fc7e0bf.1786884824.git.zhilinz@nebusec.ai/

 net/netfilter/ipvs/ip_vs_lblc.c  | 3 +++
 net/netfilter/ipvs/ip_vs_lblcr.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/net/netfilter/ipvs/ip_vs_lblc.c b/net/netfilter/ipvs/ip_vs_lblc.c
index 693bcc82ccb77..106eae24d3111 100644
--- a/net/netfilter/ipvs/ip_vs_lblc.c
+++ b/net/netfilter/ipvs/ip_vs_lblc.c
@@ -204,6 +204,9 @@ ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
 			return en;
 		ip_vs_lblc_del(en);
 	}
+	if (atomic_read(&tbl->entries) > tbl->max_size)
+		return NULL;
+
 	en = kmalloc_obj(*en, GFP_ATOMIC);
 	if (!en)
 		return NULL;
diff --git a/net/netfilter/ipvs/ip_vs_lblcr.c b/net/netfilter/ipvs/ip_vs_lblcr.c
index f53f05ceea36f..6e76808063d69 100644
--- a/net/netfilter/ipvs/ip_vs_lblcr.c
+++ b/net/netfilter/ipvs/ip_vs_lblcr.c
@@ -363,6 +363,9 @@ ip_vs_lblcr_new(struct ip_vs_lblcr_table *tbl, const union nf_inet_addr *daddr,
 
 	en = ip_vs_lblcr_get(af, tbl, daddr);
 	if (!en) {
+		if (atomic_read(&tbl->entries) > tbl->max_size)
+			return NULL;
+
 		en = kmalloc_obj(*en, GFP_ATOMIC);
 		if (!en)
 			return NULL;
-- 
2.43.0