WARNING in hfs_bnode_create

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
f2d285669aae656dfeafa0bf25e86bbbc5d22329 (Tue Apr 3 17:45:39 2018 +0000)
Merge tag 'pm-4.17-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=a19ca73b21fe8bc69101

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5003601122426880
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5963421623255040
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5236399087288320
Kernel config: https://syzkaller.appspot.com/x/.config?id=686016073509112605
compiler: gcc (GCC) 7.1.1 20170620

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Reported-by: syzbot+a19ca73b21fe8bc69101@xxxxxxxxxxxxxxxxxxxxxxxxx
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hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
hfs: new node 0 already hashed?
WARNING: CPU: 0 PID: 4477 at fs/hfs/bnode.c:416  
hfs_bnode_create+0x30b/0x380 fs/hfs/bnode.c:415
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4477 Comm: syzkaller579848 Not tainted 4.16.0+ #13
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1a7/0x27d lib/dump_stack.c:53
 panic+0x1f8/0x42c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x1f4/0x2b0 lib/bug.c:186
 fixup_bug.part.10+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:991
RIP: 0010:hfs_bnode_create+0x30b/0x380 fs/hfs/bnode.c:415
RSP: 0018:ffff8801ad477730 EFLAGS: 00010286
RAX: 000000000000001f RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000001f RSI: 1ffff10035a8ee9b RDI: ffffed0035a8eeda
RBP: ffff8801ad477770 R08: ffffed003b604f99 R09: ffffed003b604f99
R10: 0000000000000001 R11: ffffed003b604f98 R12: ffff8801d953ead0
R13: ffff8801d953ea00 R14: ffff8801d0811c00 R15: 0000000000000000
 hfs_bmap_alloc+0x804/0xee0 fs/hfs/btree.c:279
 hfs_bnode_split+0xc0/0xfb0 fs/hfs/brec.c:240
 hfs_brec_insert+0x366/0xb90 fs/hfs/brec.c:101
 hfs_cat_create+0xa06/0xd80 fs/hfs/catalog.c:123
 hfs_mkdir+0x6a/0xd0 fs/hfs/dir.c:237
 vfs_mkdir+0x390/0x600 fs/namei.c:3806
 do_mkdirat+0x224/0x2b0 fs/namei.c:3829
 SYSC_mkdir fs/namei.c:3845 [inline]
 SyS_mkdir+0x22/0x30 fs/namei.c:3843
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x440739
RSP: 002b:00007ffe4d841778 EFLAGS: 00000207 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440739
RDX: 0000000000401030 RSI: 0000000000000021 RDI: 0000000020000180
RBP: 0000000000000003 R08: 000000000000000a R09: 6f6f6c2f7665642f
R10: 0000000020011700 R11: 0000000000000207 R12: 0000000000000004
R13: 0000000000401fb0 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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