Re: [PATCH 6.12.y] netfilter: conntrack: add missing netlink policy validations

[Pablo Neira Ayuso]

Why only 6.12?

On Mon, Apr 13, 2026 at 03:31:05PM +0800, Li hongliang wrote:
> From: Florian Westphal <fw@xxxxxxxxx>
> 
> [ 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@xxxxxxxxx>
> Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
> Signed-off-by: Li hongliang <1468888505@xxxxxxx>
> ---
>  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 323e147fe282..f51cdfba68fb 100644
> --- a/net/netfilter/nf_conntrack_netlink.c
> +++ b/net/netfilter/nf_conntrack_netlink.c
> @@ -3460,7 +3460,7 @@ 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 4cc97f971264..fabb2c1ca00a 100644
> --- a/net/netfilter/nf_conntrack_proto_sctp.c
> +++ b/net/netfilter/nf_conntrack_proto_sctp.c
> @@ -587,7 +587,8 @@ 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 },
>  };
> -- 
> 2.34.1
> 
>