general protection fault in __radix_tree_delete

[syzbot <syzbot+549decbd1891d501b6d5@syzkaller.appspotmail.com>]

Hello,

syzbot hit the following crash on upstream commit
cdface5209349930ae1b51338763c8e029971b97 (Sun Apr 29 03:07:21 2018 +0000)
Merge tag 'for_linus_stable' of  
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=549decbd1891d501b6d5

So far this crash happened 8 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6647588371562496
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=4781854846615552
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4580574157078528
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=7043958930931867332
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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Reported-by: syzbot+549decbd1891d501b6d5@syzkaller.appspotmail.com
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kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4525 Comm: syz-executor786 Not tainted 4.17.0-rc2+ #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:__radix_tree_delete+0x74/0x230 lib/radix-tree.c:1989
RSP: 0018:ffff8801d9137108 EFLAGS: 00010206
RAX: 0000000000000003 RBX: dffffc0000000000 RCX: 1ffff1003b226e3e
RDX: 0000000000000000 RSI: ffffffff8768eeed RDI: ffff8801a7dac168
RBP: ffff8801d91371a8 R08: ffff8801d962c1c0 R09: ffffed0034fb5811
R10: ffff8801d91372b8 R11: ffff8801a7dac08f R12: 0000000000000000
R13: ffff8801a7dac168 R14: 0000000000000018 R15: ffff8801d9137230
FS:  0000000001df3880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000100 CR3: 00000001d9104000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  radix_tree_delete_item+0x148/0x2d0 lib/radix-tree.c:2050
  idr_remove+0x46/0x60 lib/idr.c:157
  kvm_hv_eventfd_deassign arch/x86/kvm/hyperv.c:1433 [inline]
  kvm_vm_ioctl_hv_eventfd+0x1df/0x24b arch/x86/kvm/hyperv.c:1451
  kvm_arch_vm_ioctl+0x155e/0x2690 arch/x86/kvm/x86.c:4563
  kvm_vm_ioctl+0x246/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3100
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:500 [inline]
  do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
  __do_sys_ioctl fs/ioctl.c:708 [inline]
  __se_sys_ioctl fs/ioctl.c:706 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440069
RSP: 002b:00007ffcf0b02cd8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 6d766b2f7665642f RCX: 0000000000440069
RDX: 0000000020000000 RSI: 000000004018aebd RDI: 00000000000000a9
RBP: 00000000006cb018 R08: 00007ffcf0b02cf0 R09: 00007ffcf0b02cf0
R10: 00007ffcf0b02cf0 R11: 0000000000000217 R12: 00000000004018a0
R13: 0000000000401930 R14: 0000000000000000 R15: 0000000000000000
Code: 3f 9a 88 48 c7 45 88 80 ee 68 87 c7 00 f1 f1 f1 f1 c7 40 04 00 f2 f2  
f2 c7 40 08 f3 f3 f3 f3 e8 a3 51 10 fa 4c 89 f0 48 c1 e8 03 <80> 3c 18 00  
0f 85 97 01 00 00 48 8d 55 d8 4c 8d 7a c0 49 8b 1e
RIP: __read_once_size include/linux/compiler.h:188 [inline] RSP:  
ffff8801d9137108
RIP: __radix_tree_delete+0x74/0x230 lib/radix-tree.c:1989 RSP:  
ffff8801d9137108
---[ end trace 79327005f044daef ]---


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