netfilter: flowtable: validate vlan header

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@syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
index 88787b45e30d6bffe2c6d6db2f556163e9094c3d..8b541a080342060ceceb588f489e26fe5aa8c9ff 100644 (file)
--- 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, skb_mac_offset(skb) + sizeof(*veth)))
+                       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 c2c005234dcd385a1377f3ab34c27f82d9b18b0c..98edcaa37b38d46f8236dd5ef1dff569581b8777 100644 (file)
--- 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, skb_mac_offset(skb) + sizeof(*veth)))
+                       return false;
+
                veth = (struct vlan_ethhdr *)skb_mac_header(skb);
                if (veth->h_vlan_encapsulated_proto == proto) {
                        *offset += VLAN_HLEN;