netfilter: nft_payload: rebuild vlan header on h_proto access

[ Upstream commit af84f9e447a65b4b9f79e7e5d69e19039b431c56 ]

nft can perform merging of adjacent payload requests.
This means that:

ether saddr 00:11 ... ether type 8021ad ...

is a single payload expression, for 8 bytes, starting at the
ethernet source offset.

Check that offset+length is fully within the source/destination mac
addersses.

This bug prevents 'ether type' from matching the correct h_proto in case
vlan tag got stripped.

Fixes: de6843be3082 ("netfilter: nft_payload: rebuild vlan header when needed")
Reported-by: David Ward <david.ward@ll.mit.edu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Stable-dep-of: 33c563ebf8d3 ("netfilter: nft_payload: skbuff vlan metadata mangle support")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index b1745304dbd22bd33b4c0014e33f5cffe04b74e0..697566e4ae7590718a2fbc7e0c8b15a7af2599d3 100644 (file)
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -110,6 +110,17 @@ static int nft_payload_inner_offset(const struct nft_pktinfo *pkt)
        return pkt->inneroff;
 }
 
+static bool nft_payload_need_vlan_copy(const struct nft_payload *priv)
+{
+       unsigned int len = priv->offset + priv->len;
+
+       /* data past ether src/dst requested, copy needed */
+       if (len > offsetof(struct ethhdr, h_proto))
+               return true;
+
+       return false;
+}
+
 void nft_payload_eval(const struct nft_expr *expr,
                      struct nft_regs *regs,
                      const struct nft_pktinfo *pkt)
@@ -128,7 +139,7 @@ void nft_payload_eval(const struct nft_expr *expr,
                        goto err;
 
                if (skb_vlan_tag_present(skb) &&
-                   priv->offset >= offsetof(struct ethhdr, h_proto)) {
+                   nft_payload_need_vlan_copy(priv)) {
                        if (!nft_payload_copy_vlan(dest, skb,
                                                   priv->offset, priv->len))
                                goto err;