5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit 23f3770e1a53e6c7a553135011f547209e141e72 ]
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 yusuke.suzuki@isovalent.com Reported-by: Julian Wiedmann jwi@isovalent.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Cc: Martin KaFai Lau martin.lau@kernel.org Cc: Jakub Kicinski kuba@kernel.org Cc: Jordan Rife jrife@google.com Reviewed-by: Simon Horman horms@kernel.org Reviewed-by: Jordan Rife jrife@google.com Reviewed-by: Jakub Kicinski kuba@kernel.org Reviewed-by: Martin KaFai Lau martin.lau@kernel.org Link: https://lore.kernel.org/r/20251003073418.291171-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c index b95af925b9c27..1403829b96db9 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2257,6 +2257,7 @@ 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; @@ -2364,6 +2365,7 @@ 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); }