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    SubjectRe: general protection fault in __radix_tree_delete
    On Sun, Apr 29, 2018 at 7:00 PM, syzbot
    <syzbot+549decbd1891d501b6d5@syzkaller.appspotmail.com> wrote:
    > 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)
    >
    > IMPORTANT: if you fix the bug, please add the following tag to the commit:
    > Reported-by: syzbot+549decbd1891d501b6d5@syzkaller.appspotmail.com
    > It will help syzbot understand when the bug is fixed. See footer for
    > details.
    > If you forward the report, please keep this part and the footer.


    This crash was bisected as introduced by:

    commit faeb7833eee0d6afe0ecb6bdfa6042556c2c352e
    Author: Roman Kagan <rkagan@virtuozzo.com>
    Date: Thu Feb 1 16:48:32 2018 +0300

    kvm: x86: hyperv: guest->host event signaling via eventfd

    https://gist.githubusercontent.com/dvyukov/df4971d7dfd1b37bedb5bfa0c95f9ebc/raw/ee8b7804788049f80625563e0322090c798c4544/gistfile1.txt



    > 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 ]---
    >
    >
    > ---
    > This bug is generated by a dumb bot. It may contain errors.
    > See https://goo.gl/tpsmEJ for details.
    > Direct all questions to syzkaller@googlegroups.com.
    >
    > syzbot will keep track of this bug report.
    > If you forgot to add the Reported-by tag, once the fix for this bug is
    > merged
    > into any tree, please reply to this email with:
    > #syz fix: exact-commit-title
    > If you want to test a patch for this bug, please reply with:
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    > and provide the patch inline or as an attachment.
    > To mark this as a duplicate of another syzbot report, please reply with:
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