Re: [PATCH net 3/3] netfilter: flowtable: validate vlan header
From: Eric Dumazet <edumazet@google.com>
Date: 2024-08-22 06:40:11
Also in:
netfilter-devel
On Thu, Aug 22, 2024 at 2:17 AM Pablo Neira Ayuso [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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> --- 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);
Is skb_mac_header(skb) always pointing at skb->data - 14 at this stage ? Otherwise, using if (!pskb_may_pull(skb, skb_mac_offset(skb) + sizeof(*veth)) would be safer.