From f5ecaa7ea7686fa7ecdb6affc9d3a9a42e4524b1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 24 Jul 2026 07:29:01 +0000 Subject: [PATCH] net: do not send ICMP/NDISC Redirects when peer allocation fails [ Upstream commit dbc3791e3b2472e1ccc08947e0f83b443470ff4f ] When inet_getpeer_v4() or inet_getpeer_v6() fails to allocate a peer entry under memory pressure or tree size caps, redirect handlers previously fell back to sending un-rate-limited ICMP/NDISC Redirect messages. In IPv4, ip_rt_send_redirect() called icmp_send() directly when peer == NULL. In IPv6, ip6_forward() and ndisc_send_redirect() passed a NULL peer into inet_peer_xrlim_allow(), which returned true when peer == NULL. Because ICMP/NDISC Redirects are not part of the default global rate limit mask (sysctl_icmp_ratemask), sending redirects when peer == NULL creates an un-rate-limited ICMP packet storm. Fix this by failing closed in ip_rt_send_redirect(), ip6_forward(), and ndisc_send_redirect() when peer is NULL. Fixes: 92d868292634 ("inetpeer: Move ICMP rate limiting state into inet_peer entries.") Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260724072901.1633601-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/route.c | 2 -- net/ipv6/ip6_output.c | 2 +- net/ipv6/ndisc.c | 2 ++ 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index f134c59f839e..834ec1f34e50 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -902,8 +902,6 @@ void ip_rt_send_redirect(struct sk_buff *skb) peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr, vif); if (!peer) { rcu_read_unlock(); - icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, - rt_nexthop(rt, ip_hdr(skb)->daddr)); return; } diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 2e2cd0e0d48a..5ee625d81942 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -625,7 +625,7 @@ int ip6_forward(struct sk_buff *skb) /* Limit redirects both by destination (here) and by source (inside ndisc_send_redirect) */ - if (inet_peer_xrlim_allow(peer, 1*HZ)) + if (peer && inet_peer_xrlim_allow(peer, 1*HZ)) ndisc_send_redirect(skb, target); rcu_read_unlock(); } else { diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 342e7066f765..8adb31804f01 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1731,6 +1731,8 @@ void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target) rcu_read_lock(); peer = inet_getpeer_v6(net->ipv6.peers, &ipv6_hdr(skb)->saddr); + if (!peer) + goto release; ret = inet_peer_xrlim_allow(peer, 1*HZ); rcu_read_unlock();