[PATCH 6.19 133/220] netfilter: conntrack: add missing netlink policy validations

Greg Kroah-Hartman
2026-03-23T13:56:10Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit f900e1d77ee0ef87bfb5ab3fe60f0b3d8ad5ba05 ]

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 <imv4bel@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 f261dd48973fe..d9f33a6c807c8 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -3488,7 +3488,7 @@ 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 7c6f7c9f73320..645d2c43ebf7a 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 },
};
--
2.51.0