net: lapb: increase LAPB_HEADER_LEN

In the Linux kernel, the following vulnerability has been resolved:

net: lapb: increase LAPB_HEADER_LEN

It is unclear if net/lapb code is supposed to be ready for 8021q.

We can at least avoid crashes like the following :

skbuff: skb_under_panic: text:ffffffff8aabe1f6 len:24 put:20 head:ffff88802824a400 data:ffff88802824a3fe tail:0x16 end:0x140 dev:nr0.2

------------[ cut here ]------------

kernel BUG at net/core/skbuff.c:206 !

Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI

CPU: 1 UID: 0 PID: 5508 Comm: dhcpcd Not tainted 6.12.0-rc7-syzkaller-00144-g66418447d27b #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024

RIP: 0010:skb_panic net/core/skbuff.c:206 [inline]

RIP: 0010:skb_under_panic+0x14b/0x150 net/core/skbuff.c:216

Code: 0d 8d 48 c7 c6 2e 9e 29 8e 48 8b 54 24 08 8b 0c 24 44 8b 44 24 04 4d 89 e9 50 41 54 41 57 41 56 e8 1a 6f 37 02 48 83 c4 20 90 <0f> 0b 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3

RSP: 0018:ffffc90002ddf638 EFLAGS: 00010282

RAX: 0000000000000086 RBX: dffffc0000000000 RCX: 7a24750e538ff600

RDX: 0000000000000000 RSI: 0000000000000201 RDI: 0000000000000000

RBP: ffff888034a86650 R08: ffffffff8174b13c R09: 1ffff920005bbe60

R10: dffffc0000000000 R11: fffff520005bbe61 R12: 0000000000000140

R13: ffff88802824a400 R14: ffff88802824a3fe R15: 0000000000000016

FS: 00007f2a5990d740(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000000110c2631fd CR3: 0000000029504000 CR4: 00000000003526f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

skb_push+0xe5/0x100 net/core/skbuff.c:2636

nr_header+0x36/0x320 net/netrom/nr_dev.c:69

dev_hard_header include/linux/netdevice.h:3148 [inline]

vlan_dev_hard_header+0x359/0x480 net/8021q/vlan_dev.c:83

dev_hard_header include/linux/netdevice.h:3148 [inline]

lapbeth_data_transmit+0x1f6/0x2a0 drivers/net/wan/lapbether.c:257

lapb_data_transmit+0x91/0xb0 net/lapb/lapb_iface.c:447

lapb_transmit_buffer+0x168/0x1f0 net/lapb/lapb_out.c:149

lapb_establish_data_link+0x84/0xd0

lapb_device_event+0x4e0/0x670

notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93

__dev_notify_flags+0x207/0x400

dev_change_flags+0xf0/0x1a0 net/core/dev.c:8922

devinet_ioctl+0xa4e/0x1aa0 net/ipv4/devinet.c:1188

inet_ioctl+0x3d7/0x4f0 net/ipv4/af_inet.c:1003

sock_do_ioctl+0x158/0x460 net/socket.c:1227

sock_ioctl+0x626/0x8e0 net/socket.c:1346

vfs_ioctl fs/ioctl.c:51 [inline]

__do_sys_ioctl fs/ioctl.c:907 [inline]

__se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83