Commit c6dd1aa2 authored by Fabian Bläse's avatar Fabian Bläse Committed by Jakub Kicinski
Browse files

icmp: fix icmp_ndo_send address translation for reply direction 



The icmp_ndo_send function was originally introduced to ensure proper
rate limiting when icmp_send is called by a network device driver,
where the packet's source address may have already been transformed
by SNAT.

However, the original implementation only considers the
IP_CT_DIR_ORIGINAL direction for SNAT and always replaced the packet's
source address with that of the original-direction tuple. This causes
two problems:

1. For SNAT:
   Reply-direction packets were incorrectly translated using the source
   address of the CT original direction, even though no translation is
   required.

2. For DNAT:
   Reply-direction packets were not handled at all. In DNAT, the original
   direction's destination is translated. Therefore, in the reply
   direction the source address must be set to the reply-direction
   source, so rate limiting works as intended.

Fix this by using the connection direction to select the correct tuple
for source address translation, and adjust the pre-checks to handle
reply-direction packets in case of DNAT.

Additionally, wrap the `ct->status` access in READ_ONCE(). This avoids
possible KCSAN reports about concurrent updates to `ct->status`.

Fixes: 0b41713b ("icmp: introduce helper for nat'd source address in network device context")
Signed-off-by: default avatarFabian Bläse <fabian@blaese.de>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 7000f4fa

net/ipv4/icmp.c

+4 −2
Original line number Diff line number Diff line
@@ -799,11 +799,12 @@ void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
	struct sk_buff *cloned_skb = NULL;

	struct ip_options opts = { 0 };

	enum ip_conntrack_info ctinfo;

	enum ip_conntrack_dir dir;

	struct nf_conn *ct;

	__be32 orig_ip;



	ct = nf_ct_get(skb_in, &ctinfo);

	if (!ct || !(ct->status & IPS_SRC_NAT)) {

	if (!ct || !(READ_ONCE(ct->status) & IPS_NAT_MASK)) {

		__icmp_send(skb_in, type, code, info, &opts);

		return;

	}
@@ -818,7 +819,8 @@ void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
		goto out;



	orig_ip = ip_hdr(skb_in)->saddr;

	ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;

	dir = CTINFO2DIR(ctinfo);

	ip_hdr(skb_in)->saddr = ct->tuplehash[dir].tuple.src.u3.ip;

	__icmp_send(skb_in, type, code, info, &opts);

	ip_hdr(skb_in)->saddr = orig_ip;

out:

net/ipv6/ip6_icmp.c

+4 −2
Original line number Diff line number Diff line
@@ -54,11 +54,12 @@ void icmpv6_ndo_send(struct sk_buff *skb_in, u8 type, u8 code, __u32 info) 
	struct inet6_skb_parm parm = { 0 };

	struct sk_buff *cloned_skb = NULL;

	enum ip_conntrack_info ctinfo;

	enum ip_conntrack_dir dir;

	struct in6_addr orig_ip;

	struct nf_conn *ct;



	ct = nf_ct_get(skb_in, &ctinfo);

	if (!ct || !(ct->status & IPS_SRC_NAT)) {

	if (!ct || !(READ_ONCE(ct->status) & IPS_NAT_MASK)) {

		__icmpv6_send(skb_in, type, code, info, &parm);

		return;

	}
@@ -73,7 +74,8 @@ void icmpv6_ndo_send(struct sk_buff *skb_in, u8 type, u8 code, __u32 info) 
		goto out;



	orig_ip = ipv6_hdr(skb_in)->saddr;

	ipv6_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.in6;

	dir = CTINFO2DIR(ctinfo);

	ipv6_hdr(skb_in)->saddr = ct->tuplehash[dir].tuple.src.u3.in6;

	__icmpv6_send(skb_in, type, code, info, &parm);

	ipv6_hdr(skb_in)->saddr = orig_ip;

out: