netfilter: nfnetlink_queue: fix OOB when mac header was cleared
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: 2c38de4c ("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>
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