L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
==================================================================
BUG: KASAN: slab-out-of-bounds in search_memslots include/linux/kvm_host.h:1051 [inline]
BUG: KASAN: slab-out-of-bounds in __gfn_to_memslot include/linux/kvm_host.h:1063 [inline]
BUG: KASAN: slab-out-of-bounds in __kvm_gfn_to_hva_cache_init+0x5fb/0x670 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2443
Read of size 8 at addr ffff8880a6919468 by task syz-executor754/7081

CPU: 1 PID: 7081 Comm: syz-executor754 Not tainted 5.7.0-rc1-next-20200415-syzkaller #0
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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:382
 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 search_memslots include/linux/kvm_host.h:1051 [inline]
 __gfn_to_memslot include/linux/kvm_host.h:1063 [inline]
 __kvm_gfn_to_hva_cache_init+0x5fb/0x670 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2443
 kvm_lapic_set_vapic_addr+0x88/0x180 arch/x86/kvm/lapic.c:2662
 kvm_arch_vcpu_ioctl+0xf0d/0x2c00 arch/x86/kvm/x86.c:4386
 kvm_vcpu_ioctl+0x866/0xe60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3291
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x4458b9
Code: e8 bc b7 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 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f88a031cdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 00000000004458b9
RDX: 0000000020000080 RSI: 000000004008ae93 RDI: 0000000000000005
RBP: 00000000006dac40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac4c
R13: 00007ffea1d76e4f R14: 00007f88a031d9c0 R15: 20c49ba5e353f7cf

Allocated by task 7081:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468
 kmalloc_node include/linux/slab.h:578 [inline]
 kvmalloc_node+0x61/0xf0 mm/util.c:574
 kvmalloc include/linux/mm.h:757 [inline]
 kvzalloc include/linux/mm.h:765 [inline]
 kvm_dup_memslots arch/x86/kvm/../../../virt/kvm/kvm_main.c:1101 [inline]
 kvm_set_memslot+0x115/0x1530 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1118
 __kvm_set_memory_region+0xcf7/0x1320 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1300
 __x86_set_memory_region+0x2a3/0x5a0 arch/x86/kvm/x86.c:9856
 alloc_apic_access_page arch/x86/kvm/vmx/vmx.c:3540 [inline]
 vmx_create_vcpu+0x2107/0x2b40 arch/x86/kvm/vmx/vmx.c:6799
 kvm_arch_vcpu_create+0x6ef/0xb80 arch/x86/kvm/x86.c:9376
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3030 [inline]
 kvm_vm_ioctl+0x1614/0x2400 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3585
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a6919000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1128 bytes inside of
 2048-byte region [ffff8880a6919000, ffff8880a6919800)
The buggy address belongs to the page:
page:ffffea00029a4640 refcount:1 mapcount:0 mapping:00000000fd8e7e36 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002696888 ffffea0002841948 ffff8880aa000e00
raw: 0000000000000000 ffff8880a6919000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a6919300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880a6919380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a6919400: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
                                                          ^
 ffff8880a6919480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a6919500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================