netfilter: bpf: reject invalid NAT manipulation types

As bpf_ct_set_nat_info() is not validating the NAT manipulation type a
wrong value can be passed directly to nf_nat_setup_info(). This triggers
the WARN_ON() at nf_nat_setup_info() and if panic_on_warn isn't set,
then IPS_SRC_NAT_DONE is set without adding nat_bysource and conntrack
cleanup tries to unlink an uninitialized hlist node.

Fix this by checking that NAT manipulation type is correct before
calling nf_nat_setup_info(). In addition, if the WARN_ON is hit, return
NF_DROP instead of continuing with the processing to avoid similar
situations in the future.

Reported-by: VEGA <[email protected]>
Fixes: 0fabd2aa19 ("net: netfilter: add bpf_ct_set_nat_info kfunc helper")
Signed-off-by: Fernando Fernandez Mancera <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

net/netfilter/nf_nat_bpf.c

@@ -39,6 +39,9 @@ __bpf_kfunc int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
 	if (proto != NFPROTO_IPV4 && proto != NFPROTO_IPV6)
 		return -EINVAL;
 
+	if (manip != NF_NAT_MANIP_SRC && manip != NF_NAT_MANIP_DST)
+		return -EINVAL;
+
 	memset(&range, 0, sizeof(struct nf_nat_range2));
 	range.flags = NF_NAT_RANGE_MAP_IPS;
 	range.min_addr = *addr;

net/netfilter/nf_nat_core.c

@@ -767,8 +767,9 @@ nf_nat_setup_info(struct nf_conn *ct,
 	if (nf_ct_is_confirmed(ct))
 		return NF_ACCEPT;
 
-	WARN_ON(maniptype != NF_NAT_MANIP_SRC &&
-		maniptype != NF_NAT_MANIP_DST);
+	if (WARN_ON(maniptype != NF_NAT_MANIP_SRC &&
+		    maniptype != NF_NAT_MANIP_DST))
+		return NF_DROP;
 
 	if (WARN_ON(nf_nat_initialized(ct, maniptype)))
 		return NF_DROP;