Subject: [PATCH net 02/11] netfilter: conntrack: add missing netlink policy validations

From: Florian Westphal <[email-masked]>
Date: Fri, 13 Mar 2026 16:06:05 +0100

Hyunwoo Kim reports out-of-bounds access in sctp and ctnetlink.

These attributes are used by the kernel without any validation.
Extend the netlink policies accordingly.

Quoting the reporter:
  nlattr_to_sctp() assigns the user-supplied CTA_PROTOINFO_SCTP_STATE
  value directly to ct->proto.sctp.state without checking that it is
  within the valid range. [..]

  and: ... with exp->dir = 100, the access at
  ct->master->tuplehash[100] reads 5600 bytes past the start of a
  320-byte nf_conn object, causing a slab-out-of-bounds read confirmed by
  UBSAN.

Fixes: 076a0ca02644 ("netfilter: ctnetlink: add NAT support for expectations")
Fixes: a258860e01b8 ("netfilter: ctnetlink: add full support for SCTP to ctnetlink")
Reported-by: Hyunwoo Kim <[email-masked]>
Signed-off-by: Florian Westphal <[email-masked]>
---
 net/netfilter/nf_conntrack_netlink.c    | 2 +-
 net/netfilter/nf_conntrack_proto_sctp.c | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 65aa44a12d01..c156574e1273 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -3489,7 +3489,7 @@ ctnetlink_change_expect(struct nf_conntrack_expect *x,
 
 #if IS_ENABLED(CONFIG_NF_NAT)
 static const struct nla_policy exp_nat_nla_policy[CTA_EXPECT_NAT_MAX+1] = {
-	[CTA_EXPECT_NAT_DIR]	= { .type = NLA_U32 },
+	[CTA_EXPECT_NAT_DIR]	= NLA_POLICY_MAX(NLA_BE32, IP_CT_DIR_REPLY),
 	[CTA_EXPECT_NAT_TUPLE]	= { .type = NLA_NESTED },
 };
 #endif
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 7c6f7c9f7332..645d2c43ebf7 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -582,7 +582,8 @@ static int sctp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
 }
 
 static const struct nla_policy sctp_nla_policy[CTA_PROTOINFO_SCTP_MAX+1] = {
-	[CTA_PROTOINFO_SCTP_STATE]	    = { .type = NLA_U8 },
+	[CTA_PROTOINFO_SCTP_STATE]	    = NLA_POLICY_MAX(NLA_U8,
+							 SCTP_CONNTRACK_HEARTBEAT_SENT),
 	[CTA_PROTOINFO_SCTP_VTAG_ORIGINAL]  = { .type = NLA_U32 },
 	[CTA_PROTOINFO_SCTP_VTAG_REPLY]     = { .type = NLA_U32 },
 };
-- 
2.52.0