ipvlan: Fix out-of-bound bugs caused by unset skb->mac_header

Summary

In the Linux kernel, the following vulnerability has been resolved: ipvlan: Fix out-of-bound bugs caused by unset skb->mac_header If an AF_PACKET socket is used to send packets through ipvlan and the default xmit function of the AF_PACKET socket is changed from dev_queue_xmit() to packet_direct_xmit() via setsockopt() with the option name of PACKET_QDISC_BYPASS, the skb->mac_header may not be reset and remains as the initial value of 65535, this may trigger slab-out-of-bounds bugs as following: ================================================================= UG: KASAN: slab-out-of-bounds in ipvlan_xmit_mode_l2+0xdb/0x330 [ipvlan] PU: 2 PID: 1768 Comm: raw_send Kdump: loaded Not tainted 6.0.0-rc4+ #6 ardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 all Trace: print_address_description.constprop.0+0x1d/0x160 print_report.cold+0x4f/0x112 kasan_report+0xa3/0x130 ipvlan_xmit_mode_l2+0xdb/0x330 [ipvlan] ipvlan_start_xmit+0x29/0xa0 [ipvlan] __dev_direct_xmit+0x2e2/0x380 packet_direct_xmit+0x22/0x60 packet_snd+0x7c9/0xc40 sock_sendmsg+0x9a/0xa0 __sys_sendto+0x18a/0x230 __x64_sys_sendto+0x74/0x90 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd The root cause is: 1. packet_snd() only reset skb->mac_header when sock->type is SOCK_RAW and skb->protocol is not specified as in packet_parse_headers() 2. packet_direct_xmit() doesn't reset skb->mac_header as dev_queue_xmit() In this case, skb->mac_header is 65535 when ipvlan_xmit_mode_l2() is called. So when ipvlan_xmit_mode_l2() gets mac header with eth_hdr() which use "skb->head + skb->mac_header", out-of-bound access occurs. This patch replaces eth_hdr() with skb_eth_hdr() in ipvlan_xmit_mode_l2() and reset mac header in multicast to solve this out-of-bound bug.