------------[ cut here ]------------
WARNING: CPU: 0 PID: 5958 at drivers/net/tun.c:1744 tun_get_user+0x2de3/0x36d0 drivers/net/tun.c:1743
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 5958 Comm: syz-executor0 Not tainted 4.14.0-rc5-mm1+ #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1c4/0x1e0 kernel/panic.c:546
 report_bug+0x211/0x2d0 lib/bug.c:183
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
 do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:tun_get_user+0x2de3/0x36d0 drivers/net/tun.c:1743
RSP: 0018:ffff8801c73cf730 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: ffff8801cfc5ca98 RCX: dffffc0000000000
RDX: ffffffff87024180 RSI: 0000000000000000 RDI: 0000000000000282
RBP: ffff8801c73cfae0 R08: 0000000000000001 R09: 0000000000000000
R10: ffffffff87069320 R11: 0000000000000000 R12: ffff8801c7f8a840
R13: ffff8801cfc5cb08 R14: 0000000000000000 R15: ffff8801d1830d40
 tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1792
 call_write_iter include/linux/fs.h:1770 [inline]
 do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:673
 do_iter_write+0x154/0x540 fs/read_write.c:952
 vfs_writev+0x18a/0x340 fs/read_write.c:997
 do_writev+0xfc/0x2a0 fs/read_write.c:1032
 SYSC_writev fs/read_write.c:1105 [inline]
 SyS_writev+0x27/0x30 fs/read_write.c:1102
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x452741
RSP: 002b:00007fac1be0ab10 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000002015b000 RCX: 0000000000452741
RDX: 0000000000000002 RSI: 00007fac1be0ab60 RDI: 0000000000000012
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000076 R11: 0000000000000293 R12: 00000000006f3cf8
R13: 00000000ffffffff R14: 00007fac1be0b6d4 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..