* [PATCH nf] netfilter: flowtable: validate PPPoe header
@ 2024-04-09 11:54 Pablo Neira Ayuso
0 siblings, 0 replies; only message in thread
From: Pablo Neira Ayuso @ 2024-04-09 11:54 UTC (permalink / raw)
To: netfilter-devel; +Cc: syzbot+b6f07e1c07ef40199081
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>
---
include/net/netfilter/nf_flow_table.h | 12 +++++++++++-
net/netfilter/nf_flow_table_ip.c | 8 +++++---
2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index a763dd327c6e..cb2fca8075df 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 int nf_flow_pppoe_proto(struct sk_buff *skb, __be16 *inner_proto)
+{
+ if (!pskb_may_pull(skb, PPPOE_SES_HLEN))
+ return -1;
+
+ *inner_proto = __nf_flow_pppoe_proto(skb);
+
+ return 0;
+}
+
#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_ip.c b/net/netfilter/nf_flow_table_ip.c
index e45fade76409..9e9e105052da 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;
--
2.30.2
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