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SubjectBUG: unable to handle kernel paging request in coalesced_mmio_write
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Hello,

syzbot found the following crash on:

HEAD commit: abf02e29 Merge tag 'pm-5.2-rc6' of git://git.kernel.org/pu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=111932b1a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e5c77f8090a3b96b
dashboard link: https://syzkaller.appspot.com/bug?extid=983c866c3dd6efa3662a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13299fc9a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=134b2826a00000

Bisection is inconclusive: the bug happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=108f9e06a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=148f9e06a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+983c866c3dd6efa3662a@syzkaller.appspotmail.com

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: unable to handle page fault for address: ffffed12fb15ea1f
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 21fff0067 P4D 21fff0067 PUD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8945 Comm: syz-executor116 Not tainted 5.2.0-rc5+ #57
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:coalesced_mmio_write+0x28a/0x4d0
arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:83
Code: 38 d0 7c 08 84 d2 0f 85 55 02 00 00 41 8b 47 04 48 8d 14 40 49 8d 7c
d7 08 48 ba 00 00 00 00 00 fc ff df 48 89 fe 48 c1 ee 03 <80> 3c 16 00 0f
85 1b 02 00 00 48 8d 14 40 48 be 00 00 00 00 00 fc
RSP: 0018:ffff8880a045f170 EFLAGS: 00010a02
RAX: 00000000f7d5760a RBX: 0000000000000000 RCX: ffffffff81080faa
RDX: dffffc0000000000 RSI: 1ffff112fb15ea1f RDI: ffff8897d8af50f8
RBP: ffff8880a045f1c0 R08: ffff888089e483c0 R09: 0000000000000000
R10: ffffed101408be1b R11: 0000000000000003 R12: 0000000000000001
R13: ffff8880a55dbf10 R14: 0000000000000001 R15: ffff88809cac4000
FS: 000055555573a940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed12fb15ea1f CR3: 00000000a0aee000 CR4: 00000000001426f0
Call Trace:
kvm_iodevice_write include/kvm/iodev.h:54 [inline]
__kvm_io_bus_write+0x29b/0x380
arch/x86/kvm/../../../virt/kvm/kvm_main.c:3701
kvm_io_bus_write+0x15c/0x290 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3726
vcpu_mmio_write arch/x86/kvm/x86.c:5029 [inline]
write_mmio+0x175/0x4e0 arch/x86/kvm/x86.c:5391
emulator_read_write_onepage+0x429/0xd50 arch/x86/kvm/x86.c:5460
emulator_read_write+0x1b7/0x5a0 arch/x86/kvm/x86.c:5509
emulator_write_emulated+0x3c/0x50 arch/x86/kvm/x86.c:5546
segmented_write+0xf0/0x150 arch/x86/kvm/emulate.c:1446
writeback arch/x86/kvm/emulate.c:1808 [inline]
writeback+0x3f4/0x6a0 arch/x86/kvm/emulate.c:1794
x86_emulate_insn+0x1de1/0x48f0 arch/x86/kvm/emulate.c:5695
x86_emulate_instruction+0xca3/0x1c50 arch/x86/kvm/x86.c:6509
kvm_mmu_page_fault+0x370/0x1870 arch/x86/kvm/mmu.c:5430
handle_ept_violation+0x1c8/0x500 arch/x86/kvm/vmx/vmx.c:5099
vmx_handle_exit+0x280/0x1540 arch/x86/kvm/vmx/vmx.c:5861
vcpu_enter_guest+0x1174/0x5f40 arch/x86/kvm/x86.c:8035
vcpu_run arch/x86/kvm/x86.c:8099 [inline]
kvm_arch_vcpu_ioctl_run+0x423/0x1740 arch/x86/kvm/x86.c:8307
kvm_vcpu_ioctl+0x4dc/0xf90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2755
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4444e9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 1b 0c fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff46b48808 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fff46b48810 RCX: 00000000004444e9
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000402240 R09: 0000000000402240
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000405590
R13: 0000000000405620 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
CR2: ffffed12fb15ea1f
---[ end trace 84ecc85af6872381 ]---
RIP: 0010:coalesced_mmio_write+0x28a/0x4d0
arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:83
Code: 38 d0 7c 08 84 d2 0f 85 55 02 00 00 41 8b 47 04 48 8d 14 40 49 8d 7c
d7 08 48 ba 00 00 00 00 00 fc ff df 48 89 fe 48 c1 ee 03 <80> 3c 16 00 0f
85 1b 02 00 00 48 8d 14 40 48 be 00 00 00 00 00 fc
RSP: 0018:ffff8880a045f170 EFLAGS: 00010a02
RAX: 00000000f7d5760a RBX: 0000000000000000 RCX: ffffffff81080faa
RDX: dffffc0000000000 RSI: 1ffff112fb15ea1f RDI: ffff8897d8af50f8
RBP: ffff8880a045f1c0 R08: ffff888089e483c0 R09: 0000000000000000
R10: ffffed101408be1b R11: 0000000000000003 R12: 0000000000000001
R13: ffff8880a55dbf10 R14: 0000000000000001 R15: ffff88809cac4000
FS: 000055555573a940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed12fb15ea1f CR3: 00000000a0aee000 CR4: 00000000001426f0


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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