On 64bit platforms the MAC header is set to 0xffff on allocation and
also when a helper like skb_unset_mac_header() is called.
dev_parse_header may call skb_mac_header() which assumes valid mac offset:
BUG: KASAN: use-after-free in eth_header_parse+0x75/0x90
Read of size 6 at addr
ffff8881075a5c05 by task nf-queue/1364
Call Trace:
memcpy+0x20/0x60
eth_header_parse+0x75/0x90
__nfqnl_enqueue_packet+0x1a61/0x3380
__nf_queue+0x597/0x1300
nf_queue+0xf/0x40
nf_hook_slow+0xed/0x190
nf_hook+0x184/0x440
ip_output+0x1c0/0x2a0
nf_reinject+0x26f/0x700
nfqnl_recv_verdict+0xa16/0x18b0
nfnetlink_rcv_msg+0x506/0xe70
The existing code only works if the skb has a mac header.
Fixes:
2c38de4c1f8da7 ("netfilter: fix looped (broad|multi)cast's MAC handling")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
goto nla_put_failure;
if (indev && entskb->dev &&
- entskb->mac_header != entskb->network_header) {
+ skb_mac_header_was_set(entskb)) {
struct nfqnl_msg_packet_hw phw;
int len;