syzbot managed to crash a host by creating a bond
with a GRE device.

For non Ethernet device, bonding calls bond_setup_by_slave()
instead of ether_setup(), and unfortunately dev->needed_headroom
was not copied from the new added member.

[  171.243095] skbuff: skb_under_panic: text:ffffffffa184b9ea len:116 put:20 head:ffff883f84012dc0 data:ffff883f84012dbc tail:0x70 end:0xd00 dev:bond0
[  171.243111] ------------[ cut here ]------------
[  171.243112] kernel BUG at net/core/skbuff.c:112!
[  171.243117] invalid opcode: 0000 [#1] SMP KASAN PTI
[  171.243469] gsmi: Log Shutdown Reason 0x03
[  171.243505] Call Trace:
[  171.243506]  <IRQ>
[  171.243512]  [<ffffffffa171be59>] skb_push+0x49/0x50
[  171.243516]  [<ffffffffa184b9ea>] ipgre_header+0x2a/0xf0
[  171.243520]  [<ffffffffa17452d7>] neigh_connected_output+0xb7/0x100
[  171.243524]  [<ffffffffa186f1d3>] ip6_finish_output2+0x383/0x490
[  171.243528]  [<ffffffffa186ede2>] __ip6_finish_output+0xa2/0x110
[  171.243531]  [<ffffffffa186acbc>] ip6_finish_output+0x2c/0xa0
[  171.243534]  [<ffffffffa186abe9>] ip6_output+0x69/0x110
[  171.243537]  [<ffffffffa186ac90>] ? ip6_output+0x110/0x110
[  171.243541]  [<ffffffffa189d952>] mld_sendpack+0x1b2/0x2d0
[  171.243544]  [<ffffffffa189d290>] ? mld_send_report+0xf0/0xf0
[  171.243548]  [<ffffffffa189c797>] mld_ifc_timer_expire+0x2d7/0x3b0
[  171.243551]  [<ffffffffa189c4c0>] ? mld_gq_timer_expire+0x50/0x50
[  171.243556]  [<ffffffffa0fea270>] call_timer_fn+0x30/0x130
[  171.243559]  [<ffffffffa0fea17c>] expire_timers+0x4c/0x110
[  171.243563]  [<ffffffffa0fea0e3>] __run_timers+0x213/0x260
[  171.243566]  [<ffffffffa0fecb7d>] ? ktime_get+0x3d/0xa0
[  171.243570]  [<ffffffffa0ff9c4e>] ? clockevents_program_event+0x7e/0xe0
[  171.243574]  [<ffffffffa0f7e5d5>] ? sched_clock_cpu+0x15/0x190
[  171.243577]  [<ffffffffa0fe973d>] run_timer_softirq+0x1d/0x40
[  171.243581]  [<ffffffffa1c00152>] __do_softirq+0x152/0x2f0
[  171.243585]  [<ffffffffa0f44e1f>] irq_exit+0x9f/0xb0
[  171.243588]  [<ffffffffa1a02e1d>] smp_apic_timer_interrupt+0xfd/0x1a0
[  171.243591]  [<ffffffffa1a01ea6>] apic_timer_interrupt+0x86/0x90

Fixes: f5184d26 ("net: Allow netdevices to specify needed head/tailroom")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>