[PATCH 6.18 080/396] net: do not send ICMP/NDISC Redirects when peer allocation fails

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <[email protected]>

[ 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 <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 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 11d990703d31a..778467bea476a 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -892,8 +892,6 @@ 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 8f37c9cc868b0..9ef6581168f0f 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -630,7 +630,7 @@ 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 9df1fba967c6e..7262356de10d9 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1706,6 +1706,8 @@ void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target)
 	}
 
 	peer = inet_getpeer_v6(net->ipv6.peers, &ipv6_hdr(skb)->saddr);
+	if (!peer)
+		goto release;
 	ret = inet_peer_xrlim_allow(peer, 1*HZ);
 
 	if (!ret)
-- 
2.53.0