Ensure there is sufficient room to access the protocol field of the
VLAN header, validate it once before the flowtable lookup.
=====================================================
BUG: KMSAN: uninit-value in nf_flow_offload_inet_hook+0x45a/0x5f0 net/netfilter/nf_flow_table_inet.c:32
nf_flow_offload_inet_hook+0x45a/0x5f0 net/netfilter/nf_flow_table_inet.c:32
nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
nf_hook_slow+0xf4/0x400 net/netfilter/core.c:626
nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
nf_ingress net/core/dev.c:5440 [inline]
Fixes: 4cd91f7c290f ("netfilter: flowtable: add vlan support")
Reported-by: syzbot+8407d9bb88cd4c6bf61a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
ctx->offset is bumped to VLAN_HLEN to reach the IP header, check for
VLAN_HLEN instead of vlan_ethhdr.
net/netfilter/nf_flow_table_inet.c | 3 +++
net/netfilter/nf_flow_table_ip.c | 3 +++
2 files changed, 6 insertions(+)
diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
index 88787b45e30d..dd9a392052ee 100644
--- a/net/netfilter/nf_flow_table_inet.c
+++ b/net/netfilter/nf_flow_table_inet.c
@@ -17,6 +17,9 @@ nf_flow_offload_inet_hook(void *priv, struct sk_buff *skb,
switch (skb->protocol) {
case htons(ETH_P_8021Q):
+ if (!pskb_may_pull(skb, VLAN_HLEN))
+ return NF_ACCEPT;
+
veth = (struct vlan_ethhdr *)skb_mac_header(skb);
proto = veth->h_vlan_encapsulated_proto;
break;
diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index c2c005234dcd..9a9031e9ea1c 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -281,6 +281,9 @@ static bool nf_flow_skb_encap_protocol(struct sk_buff *skb, __be16 proto,
switch (skb->protocol) {
case htons(ETH_P_8021Q):
+ if (!pskb_may_pull(skb, VLAN_HLEN))
+ return false;
+
veth = (struct vlan_ethhdr *)skb_mac_header(skb);
if (veth->h_vlan_encapsulated_proto == proto) {
*offset += VLAN_HLEN;
--
2.30.2
