BUG: using __this_cpu_read() in preemptible code in ip6_finish_output

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e1427237 macsec: add noinline tag to avoid a frame size wa..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15594553200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8e9bc94c16d346a6
dashboard link: https://syzkaller.appspot.com/bug?extid=51471b4aae195285a4a3
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=156ffb07200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14412673200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+51471b4aae195285a4a3@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: using __this_cpu_read() in preemptible [00000000] code:  
syz-executor222/7596
caller is dev_recursion_level include/linux/netdevice.h:3052 [inline]
caller is ip6_skb_dst_mtu include/net/ip6_route.h:245 [inline]
caller is ip6_finish_output+0x335/0xdc0 net/ipv6/ip6_output.c:149
CPU: 1 PID: 7596 Comm: syz-executor222 Not tainted 5.1.0-rc2+ #118
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 __this_cpu_preempt_check+0x246/0x270 lib/smp_processor_id.c:47
 dev_recursion_level include/linux/netdevice.h:3052 [inline]
 ip6_skb_dst_mtu include/net/ip6_route.h:245 [inline]
 ip6_finish_output+0x335/0xdc0 net/ipv6/ip6_output.c:149
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip6_output+0x235/0x7f0 net/ipv6/ip6_output.c:171
 dst_output include/net/dst.h:433 [inline]
 NF_HOOK include/linux/netfilter.h:289 [inline]
 NF_HOOK include/linux/netfilter.h:283 [inline]
 ip6_xmit+0xe41/0x20c0 net/ipv6/ip6_output.c:275
 inet6_csk_xmit+0x2fb/0x5d0 net/ipv6/inet6_connection_sock.c:139
 __tcp_transmit_skb+0x1a32/0x3750 net/ipv4/tcp_output.c:1155
 tcp_transmit_skb net/ipv4/tcp_output.c:1171 [inline]
 tcp_send_syn_data net/ipv4/tcp_output.c:3494 [inline]
 tcp_connect+0x1e47/0x4280 net/ipv4/tcp_output.c:3533
 tcp_v6_connect+0x150b/0x20a0 net/ipv6/tcp_ipv6.c:331
 __inet_stream_connect+0x83f/0xea0 net/ipv4/af_inet.c:659
 tcp_sendmsg_fastopen net/ipv4/tcp.c:1155 [inline]
 tcp_sendmsg_locked+0x231f/0x37f0 net/ipv4/tcp.c:1197
 tcp_sendmsg+0x30/0x50 net/ipv4/tcp.c:1431
 inet_sendmsg+0x147/0x5e0 net/ipv4/af_inet.c:802
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xdd/0x130 net/socket.c:661
 __sys_sendto+0x262/0x380 net/socket.c:1932
 __do_sys_sendto net/socket.c:1944 [inline]
 __se_sys_sendto net/socket.c:1940 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1940
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440189
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffed7abd1a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440189
RDX: 0000000000000000 RSI: 0000000000000000 RD


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