[PATCH 6.8 020/158] netfilter: flowtable: validate pppoe header

Greg Kroah-Hartman
2024-04-23T21:41:00Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 87b3593bed1868b2d9fe096c01bcdf0ea86cbebf ]

Ensure there is sufficient room to access the protocol field of the
PPPoe header. Validate it once before the flowtable lookup, then use a
helper function to access protocol field.

Reported-by: syzbot+b6f07e1c07ef40199081@syzkaller.appspotmail.com
Fixes: 72efd585f714 ("netfilter: flowtable: add pppoe support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/netfilter/nf_flow_table.h | 12 +++++++++++-
net/netfilter/nf_flow_table_inet.c | 3 ++-
net/netfilter/nf_flow_table_ip.c | 8 +++++---
3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index a763dd327c6ea..9abb7ee40d72f 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -336,7 +336,7 @@ int nf_flow_rule_route_ipv6(struct net *net, struct flow_offload *flow,
int nf_flow_table_offload_init(void);
void nf_flow_table_offload_exit(void);

-static inline __be16 nf_flow_pppoe_proto(const struct sk_buff *skb)
+static inline __be16 __nf_flow_pppoe_proto(const struct sk_buff *skb)
{
__be16 proto;

@@ -352,6 +352,16 @@ static inline __be16 nf_flow_pppoe_proto(const struct sk_buff *skb)
return 0;
}

+static inline bool nf_flow_pppoe_proto(struct sk_buff *skb, __be16 *inner_proto)
+{
+ if (!pskb_may_pull(skb, PPPOE_SES_HLEN))
+ return false;
+
+ *inner_proto = __nf_flow_pppoe_proto(skb);
+
+ return true;
+}
+
#define NF_FLOW_TABLE_STAT_INC(net, count) __this_cpu_inc((net)->ft.stat->count)
#define NF_FLOW_TABLE_STAT_DEC(net, count) __this_cpu_dec((net)->ft.stat->count)
#define NF_FLOW_TABLE_STAT_INC_ATOMIC(net, count) \
diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
index 9505f9d188ff2..6eef15648b7b0 100644
--- a/net/netfilter/nf_flow_table_inet.c
+++ b/net/netfilter/nf_flow_table_inet.c
@@ -21,7 +21,8 @@ nf_flow_offload_inet_hook(void *priv, struct sk_buff *skb,
proto = veth->h_vlan_encapsulated_proto;
break;
case htons(ETH_P_PPP_SES):
- proto = nf_flow_pppoe_proto(skb);
+ if (!nf_flow_pppoe_proto(skb, &proto))
+ return NF_ACCEPT;
break;
default:
proto = skb->protocol;
diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index e45fade764096..9e9e105052dae 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -273,10 +273,11 @@ static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
return NF_STOLEN;
}

-static bool nf_flow_skb_encap_protocol(const struct sk_buff *skb, __be16 proto,
+static bool nf_flow_skb_encap_protocol(struct sk_buff *skb, __be16 proto,
u32 *offset)
{
struct vlan_ethhdr *veth;
+ __be16 inner_proto;

switch (skb->protocol) {
case htons(ETH_P_8021Q):
@@ -287,7 +288,8 @@ static bool nf_flow_skb_encap_protocol(const struct sk_buff *skb, __be16 proto,
}
break;
case htons(ETH_P_PPP_SES):
- if (nf_flow_pppoe_proto(skb) == proto) {
+ if (nf_flow_pppoe_proto(skb, &inner_proto) &&
+ inner_proto == proto) {
*offset += PPPOE_SES_HLEN;
return true;
}
@@ -316,7 +318,7 @@ static void nf_flow_encap_pop(struct sk_buff *skb,
skb_reset_network_header(skb);
break;
case htons(ETH_P_PPP_SES):
- skb->protocol = nf_flow_pppoe_proto(skb);
+ skb->protocol = __nf_flow_pppoe_proto(skb);
skb_pull(skb, PPPOE_SES_HLEN);
skb_reset_network_header(skb);
break;
--
2.43.0