From c89477ad79446867394360b29bb801010fc3ff22 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 3 Feb 2026 19:25:09 +0000 Subject: [PATCH] inet: RAW sockets using IPPROTO_RAW MUST drop incoming ICMP Yizhou Zhao reported that simply having one RAW socket on protocol IPPROTO_RAW (255) was dangerous. socket(AF_INET, SOCK_RAW, 255); A malicious incoming ICMP packet can set the protocol field to 255 and match this socket, leading to FNHE cache changes. inner = IP(src="192.168.2.1", dst="8.8.8.8", proto=255)/Raw("TEST") pkt = IP(src="192.168.1.1", dst="192.168.2.1")/ICMP(type=3, code=4, nexthopmtu=576)/inner "man 7 raw" states: A protocol of IPPROTO_RAW implies enabled IP_HDRINCL and is able to send any IP protocol that is specified in the passed header. Receiving of all IP protocols via IPPROTO_RAW is not possible using raw sockets. Make sure we drop these malicious packets. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Yizhou Zhao Link: https://lore.kernel.org/netdev/20251109134600.292125-1-zhaoyz24@mails.tsinghua.edu.cn/ Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260203192509.682208-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv4/icmp.c | 14 ++++++++++---- net/ipv6/icmp.c | 6 ++++++ 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 4abbec2f47ef5..4acbbc703e798 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -1031,16 +1031,22 @@ static void icmp_socket_deliver(struct sk_buff *skb, u32 info) /* Checkin full IP header plus 8 bytes of protocol to * avoid additional coding at protocol handlers. */ - if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { - __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS); - return; - } + if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) + goto out; + + /* IPPROTO_RAW sockets are not supposed to receive anything. */ + if (protocol == IPPROTO_RAW) + goto out; raw_icmp_error(skb, protocol, info); ipprot = rcu_dereference(inet_protos[protocol]); if (ipprot && ipprot->err_handler) ipprot->err_handler(skb, info); + return; + +out: + __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS); } static bool icmp_tag_validation(int proto) diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c index 9d37e7711bc2b..a77f3113ef23b 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -1066,6 +1066,12 @@ enum skb_drop_reason icmpv6_notify(struct sk_buff *skb, u8 type, if (reason != SKB_NOT_DROPPED_YET) goto out; + if (nexthdr == IPPROTO_RAW) { + /* Add a more specific reason later ? */ + reason = SKB_DROP_REASON_NOT_SPECIFIED; + goto out; + } + /* BUGGG_FUTURE: we should try to parse exthdrs in this packet. Without this we will not able f.e. to make source routed pmtu discovery. -- 2.47.3