Cilium has a BPF egress gateway feature which forces outgoing K8s Pod traffic to pass through dedicated egress gateways which then SNAT the traffic in order to interact with stable IPs outside the cluster. The traffic is directed to the gateway via vxlan tunnel in collect md mode. A recent BPF change utilized the bpf_redirect_neigh() helper to forward packets after the arrival and decap on vxlan, which turned out over time that the kmalloc-256 slab usage in kernel was ever-increasing. The issue was that vxlan allocates the metadata_dst object and attaches it through a fake dst entry to the skb. The latter was never released though given bpf_redirect_neigh() was merely setting the new dst entry via skb_dst_set() without dropping an existing one first. Fixes: b4ab31414970 ("bpf: Add redirect_neigh helper as redirect drop-in") Reported-by: Yusuke Suzuki Reported-by: Julian Wiedmann Signed-off-by: Daniel Borkmann Cc: Martin KaFai Lau Cc: Jakub Kicinski Cc: Jordan Rife --- net/core/filter.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index b005363f482c..c3c0b5a37504 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2281,6 +2281,7 @@ static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev, if (IS_ERR(dst)) goto out_drop; + skb_dst_drop(skb); skb_dst_set(skb, dst); } else if (nh->nh_family != AF_INET6) { goto out_drop; @@ -2389,6 +2390,7 @@ static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev, goto out_drop; } + skb_dst_drop(skb); skb_dst_set(skb, &rt->dst); } -- 2.43.0