From: Daniel Borkmann <daniel@iogearbox.net> stable inclusion from stable-v5.10.246 commit 3fba965a9aac0fa3cbd8138436a37af9ab466d79 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID6BVH CVE: CVE-2025-40183 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ 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> Signed-off-by: Wang Liang <wangliang74@huawei.com> --- net/core/filter.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index d3e64273b3c4..adacca9ee505 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2256,6 +2256,7 @@ 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; @@ -2371,6 +2372,7 @@ 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); } -- 2.34.1