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SubjectWARNING in mmu_spte_clear_track_bits (2)

syzbot found the following crash on:

HEAD commit: 6a1d293238c1 Add linux-next specific files for 20181224
git tree: linux-next
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:
C reproducer:

IMPORTANT: if you fix the bug, please add the following tag to the commit:

sshd (7857) used greatest stack depth: 15720 bytes left
L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and for details.
WARNING: CPU: 0 PID: 7873 at arch/x86/kvm/mmu.c:830
mmu_spte_clear_track_bits+0x45f/0x520 arch/x86/kvm/mmu.c:830
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7873 Comm: syz-executor226 Not tainted 4.20.0-rc7-next-20181224
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+0x1d3/0x2c6 lib/dump_stack.c:113
panic+0x2ad/0x632 kernel/panic.c:214
__warn.cold.8+0x20/0x4f kernel/panic.c:571
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:176 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:269
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:288
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:mmu_spte_clear_track_bits+0x45f/0x520 arch/x86/kvm/mmu.c:830
Code: 40 ff ff ff 31 ff 44 89 fe 48 ba 00 00 00 00 00 fc ff df c6 04 10 f8
e8 4f ad 70 00 45 85 ff 0f 85 65 fd ff ff e8 31 ac 70 00 <0f> 0b e9 59 fd
ff ff e8 25 ac 70 00 4c 89 ef e8 4d 33 f7 ff 31 f6
RSP: 0018:ffff8881b9df6860 EFLAGS: 00010293
RAX: ffff8881b1b6c3c0 RBX: 40000001af5e8c77 RCX: ffffffff81114481
RDX: 0000000000000000 RSI: ffffffff8111448f RDI: 0000000000000005
RBP: ffff8881b9df6978 R08: ffff8881b1b6c3c0 R09: fffff94000d7af46
R10: fffff94000d7af46 R11: ffffea0006bd7a37 R12: 1ffff110373bed0e
R13: 00000000001af5e8 R14: ffff8881b9df6950 R15: 0000000000000000
drop_spte+0x24/0x220 arch/x86/kvm/mmu.c:1468
mmu_page_zap_pte+0x2d3/0x3a0 arch/x86/kvm/mmu.c:2613
kvm_mmu_page_unlink_children arch/x86/kvm/mmu.c:2635 [inline]
kvm_mmu_prepare_zap_page+0x1f9/0x1530 arch/x86/kvm/mmu.c:2679
kvm_zap_obsolete_pages arch/x86/kvm/mmu.c:5843 [inline]
kvm_mmu_invalidate_zap_all_pages+0x348/0x7b0 arch/x86/kvm/mmu.c:5884
kvm_arch_flush_shadow_all+0x15/0x20 arch/x86/kvm/x86.c:9431
__mmu_notifier_release+0x1e9/0x630 mm/mmu_notifier.c:68
mmu_notifier_release include/linux/mmu_notifier.h:261 [inline]
exit_mmap+0xa1/0x590 mm/mmap.c:3088
__mmput kernel/fork.c:1045 [inline]
mmput+0x247/0x610 kernel/fork.c:1066
exit_mm kernel/exit.c:545 [inline]
do_exit+0xdcc/0x25f0 kernel/exit.c:854
do_group_exit+0x177/0x440 kernel/exit.c:970
get_signal+0x8b0/0x1980 kernel/signal.c:2515
do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
RIP: 0033:0x448c79
Code: e8 3c af 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 4b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe328b1fcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006ddc58 RCX: 0000000000448c79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006ddc58
RBP: 00000000006ddc50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ddc5c
R13: 00007ffcaa19611f R14: 00007fe328b209c0 R15: 00000000006ddd4c
Kernel Offset: disabled
Rebooting in 86400 seconds..

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