netfilter: ip6t_eui64: reject invalid MAC header for all packets

`eui64_mt6()` derives a modified EUI-64 from the Ethernet source address
and compares it with the low 64 bits of the IPv6 source address.

The existing guard only rejects an invalid MAC header when
`par->fragoff != 0`. For packets with `par->fragoff == 0`, `eui64_mt6()`
can still reach `eth_hdr(skb)` even when the MAC header is not valid.

Fix this by removing the `par->fragoff != 0` condition so that packets
with an invalid MAC header are rejected before accessing `eth_hdr(skb)`.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Ren Wei <enjou1224z@gmail.com>
Signed-off-by: Zhengchuan Liang <zcliangcn@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/net/ipv6/netfilter/ip6t_eui64.c b/net/ipv6/netfilter/ip6t_eui64.c
index d704f7ed300c24b021810251452751e982d71d03..da69a27e8332c13e0a54014f6913a7c617cc09fa 100644 (file)
--- a/net/ipv6/netfilter/ip6t_eui64.c
+++ b/net/ipv6/netfilter/ip6t_eui64.c
@@ -22,8 +22,7 @@ eui64_mt6(const struct sk_buff *skb, struct xt_action_param *par)
        unsigned char eui64[8];
 
        if (!(skb_mac_header(skb) >= skb->head &&
-             skb_mac_header(skb) + ETH_HLEN <= skb->data) &&
-           par->fragoff != 0) {
+             skb_mac_header(skb) + ETH_HLEN <= skb->data)) {
                par->hotdrop = true;
                return false;
        }