WARNING in ovl_instantiate

[syzbot <syzbot+9c69c282adc4edd2b540@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    442b8cea2477 Add linux-next specific files for 20181109
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=169a6fbd400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2f72bdb11df9fbe8
dashboard link: https://syzkaller.appspot.com/bug?extid=9c69c282adc4edd2b540
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9c69c282adc4edd2b540@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 9768 at fs/overlayfs/dir.c:263  
ovl_instantiate+0x369/0x400 fs/overlayfs/dir.c:263
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9768 Comm: syz-executor2 Not tainted 4.20.0-rc1-next-20181109+  
#110
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+0x244/0x39d lib/dump_stack.c:113
  panic+0x2ad/0x55c kernel/panic.c:188
  __warn.cold.8+0x20/0x45 kernel/panic.c:540
  report_bug+0x254/0x2d0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:178 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
  do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:ovl_instantiate+0x369/0x400 fs/overlayfs/dir.c:263
Code: c3 89 c6 e8 69 84 ee fe 85 db 0f 85 9e 00 00 00 e8 4c 83 ee fe 4c 89  
e7 45 31 f6 e8 11 18 45 ff e9 ec fe ff ff e8 37 83 ee fe <0f> 0b e9 e0 fe  
ff ff e8 2b 83 ee fe 0f 0b e9 63 ff ff ff e8 1f db
RSP: 0018:ffff88018f31f990 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff88018f31fa28 RCX: ffffc90013c02000
RDX: 000000000000a369 RSI: ffffffff82912579 RDI: 0000000000000007
RBP: ffff88018f31fa50 R08: ffff8801bb18a000 R09: ffffed0031e63ee5
R10: ffffed0031e63ee5 R11: 0000000000000003 R12: ffff8801cd1e8300
R13: ffff88018f31f9c8 R14: ffffffffffffff8c R15: 0000000000000000
  ovl_create_over_whiteout fs/overlayfs/dir.c:518 [inline]
  ovl_create_or_link+0xad6/0x1560 fs/overlayfs/dir.c:582
  ovl_create_object+0x2e9/0x3a0 fs/overlayfs/dir.c:616
  ovl_create+0x2b/0x30 fs/overlayfs/dir.c:630
  vfs_create+0x388/0x5b0 fs/namei.c:2912
  do_mknodat+0x410/0x530 fs/namei.c:3766
  __do_sys_mknod fs/namei.c:3795 [inline]
  __se_sys_mknod fs/namei.c:3793 [inline]
  __x64_sys_mknod+0x7b/0xb0 fs/namei.c:3793
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2126d09c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000085
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000340
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2126d0a6d4
R13: 00000000004c2a6e R14: 00000000004d4110 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


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