syzbot

 should_failslab+0xec/0x120 mm/failslab.c:32
 slab_pre_alloc_hook mm/slab.h:422 [inline]
 slab_alloc_node mm/slab.c:3286 [inline]
 kmem_cache_alloc_node+0x56/0x760 mm/slab.c:3629
kasan: GPF could be caused by NULL-ptr deref or user memory access
 __alloc_skb+0xf1/0x780 net/core/skbuff.c:193
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
 alloc_skb include/linux/skbuff.h:983 [inline]
 tcp_xmit_probe_skb+0x67/0x360 net/ipv4/tcp_output.c:3640
 tcp_send_window_probe+0x11d/0x150 net/ipv4/tcp_output.c:3662
CPU: 1 PID: 14630 Comm: syz-executor7 Not tainted 4.15.0+ #221
 do_tcp_setsockopt.isra.37+0xb9e/0x2130 net/ipv4/tcp.c:2684
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ip6t_do_table+0x132d/0x1a30 net/ipv6/netfilter/ip6_tables.c:355
RSP: 0018:ffff8801cd79e728 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801b3302500 RCX: ffffffff84db22a1
RDX: 0000000000000456 RSI: 0000000000000000 RDI: ffff8801b330265e
RBP: ffff8801cd79e970 R08: ffff8801cd79ea68 R09: 0000000000000002
 tcp_setsockopt+0xb0/0xd0 net/ipv4/tcp.c:2907
R10: 00000000000000d0 R11: 0000000000000000 R12: 0000000000000001
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff8801b33025d0
 SYSC_setsockopt net/socket.c:1849 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1828
FS:  00007f6b0e57b700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000207a1000 CR3: 00000001ab33c004 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007fb60509bc58 EFLAGS: 00000212
 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fb60509baa0 RCX: 0000000000453299
RDX: 0000000000000013 RSI: 0000000000000006 RDI: 0000000000000013
RBP: 00007fb60509ba90 R08: 0000000000000004 R09: 0000000000000000
R10: 000000002017f000 R11: 0000000000000212 R12: 00000000004b8096
 ip6table_security_hook+0x65/0x80 net/ipv6/netfilter/ip6table_security.c:45
R13: 00007fb60509bbc8 R14: 00000000004b8096 R15: 0000000000000000
 nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
 nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
 nf_hook include/linux/netfilter.h:243 [inline]
 NF_HOOK include/linux/netfilter.h:286 [inline]
 ip6_input+0x35c/0x560 net/ipv6/ip6_input.c:327
 ip6_mc_input+0x3a8/0xb10 net/ipv6/ip6_input.c:404
 dst_input include/net/dst.h:449 [inline]
 ip6_rcv_finish+0x297/0x8c0 net/ipv6/ip6_input.c:71
 NF_HOOK include/linux/netfilter.h:288 [inline]
 ipv6_rcv+0xf37/0x1fa0 net/ipv6/ip6_input.c:208
 __netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4547
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4612
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4686
 netif_receive_skb+0xae/0x390 net/core/dev.c:4710
 tun_rx_batched.isra.52+0x5ee/0x870 drivers/net/tun.c:1558
 tun_get_user+0x25de/0x3940 drivers/net/tun.c:1958
 tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1986
 call_write_iter include/linux/fs.h:1781 [inline]
 do_iter_readv_writev+0x55c/0x830 fs/read_write.c:653
 do_iter_write+0x154/0x540 fs/read_write.c:932
 vfs_writev+0x18a/0x340 fs/read_write.c:977
 do_writev+0xfc/0x2a0 fs/read_write.c:1012
 SYSC_writev fs/read_write.c:1085 [inline]
 SyS_writev+0x27/0x30 fs/read_write.c:1082
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453171
RSP: 002b:00007f6b0e57ab80 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453171
RDX: 0000000000000001 RSI: 00007f6b0e57abd0 RDI: 0000000000000012
RBP: 00000000000003d9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000083 R11: 0000000000000293 R12: 00000000006f4cf8
R13: 00000000ffffffff R14: 00007f6b0e57b6d4 R15: 0000000000000000
Code: 41 f6 87 83 00 00 00 04 75 37 e8 0f 83 95 fc 8b 85 14 fe ff ff 48 8b b5 50 fe ff ff 4c 8d 2c c6 44 8d 60 01 4c 89 e8 48 c1 e8 03 <42> 80 3c 30 00 0f 85 26 03 00 00 4d 89 7d 00 44 89 a5 14 fe ff 
RIP: ip6t_do_table+0x132d/0x1a30 net/ipv6/netfilter/ip6_tables.c:355 RSP: ffff8801cd79e728
---[ end trace c2f8563c30ee5480 ]---