kvm: paging fault in kvm_gfn_to_hva_cache_init

[Dmitry Vyukov]

Hello,

I've got the following crash while running syzkaller fuzzer:

BUG: unable to handle kernel paging request at ffffc90005204408
IP: [< inline >] __read_once_size include/linux/compiler.h:243
IP: [< inline >] atomic_read arch/x86/include/asm/atomic.h:26
IP: [< inline >] search_memslots include/linux/kvm_host.h:900
IP: [< inline >] __gfn_to_memslot include/linux/kvm_host.h:928
IP: [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
IP: [<ffffffff8105a299>] kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
PGD 3e90a067 [ 112.607074] PUD 6dc08067

Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 10437 Comm: syz-executor Not tainted 4.9.0-rc4+ #49
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006b8b2dc0 task.stack: ffff88006d5f0000
RIP: 0010:[<ffffffff8105a299>] [< inline >] __read_once_size
include/linux/compiler.h:243
RIP: 0010:[<ffffffff8105a299>] [< inline >] atomic_read
arch/x86/include/asm/atomic.h:26
RIP: 0010:[<ffffffff8105a299>] [< inline >] search_memslots
include/linux/kvm_host.h:900
RIP: 0010:[<ffffffff8105a299>] [< inline >] __gfn_to_memslot
include/linux/kvm_host.h:928
RIP: 0010:[<ffffffff8105a299>] [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
RIP: 0010:[<ffffffff8105a299>] [<ffffffff8105a299>]
kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
RSP: 0018:ffff88006d5f7730 EFLAGS: 00010246
RAX: 0000000000000003 RBX: 0000000000000004 RCX: ffffc900013a5000
RDX: 0000000000000000 RSI: ffff88006de32d50 RDI: ffffc900051f9000
RBP: ffff88006d5f7808 R08: ffffed000dabef36 R09: ffffed000dabef36
R10: ffffed000dabef35 R11: ffff88006d5f79af R12: ffffffffffffff6e
R13: ffff88006b290420 R14: 0000000000000001 R15: 0000000000000002
FS: 00007f6db05f1700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc90005204408 CR3: 000000003c36a000 CR4: 00000000000026e0
Stack:
1ffff1000dabeef0 ffff88006ba840c0 ffff88006d5f7750 ffffc90005204408
0000000000000001 ffff88006ba84000 0000000000000001 0000000000001000
ffff88006de32d50 ffffc900051f9000 0000000041b58ab3 ffffffff837c394f
Call Trace:
[<ffffffff8112696d>] kvm_lapic_set_vapic_addr+0xed/0x140
arch/x86/kvm/lapic.c:2217
[<ffffffff810a77e4>] kvm_arch_vcpu_ioctl+0x224/0x3100 arch/x86/kvm/x86.c:3425
[<ffffffff810608b2>] kvm_vcpu_ioctl+0x1e2/0xdd0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2708
[< inline >] vfs_ioctl fs/ioctl.c:43
[<ffffffff816b03cc>] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679
[< inline >] SYSC_ioctl fs/ioctl.c:694
[<ffffffff816b130f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
[<ffffffff831f0dc1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
Code: 03 48 b8 00 00 00 00 00 fc ff df 0f b6 14 02 48 89 f8 83 e0 07
83 c0 03 38 d0 7c 08 84 d2 0f 85 59 06 00 00 48 8b bd 70 ff ff ff <48>
63 87 08 b4 00 00 4c 8d 6f 08 48 8d 14 80 48 8d 04 50 49 8d
RIP [< inline >] __read_once_size include/linux/compiler.h:243
RIP [< inline >] atomic_read arch/x86/include/asm/atomic.h:26
RIP [< inline >] search_memslots include/linux/kvm_host.h:900
RIP [< inline >] __gfn_to_memslot include/linux/kvm_host.h:928
RIP [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
RIP [<ffffffff8105a299>] kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
RSP <ffff88006d5f7730>
CR2: ffffc90005204408
---[ end trace b42cbfdf0baf531e ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
reboot: cpu_has_vmx: ecx=80a02021 1


and another almost identical:



BUG: unable to handle kernel paging request at ffffc90005907408
IP: [< inline >] __read_once_size include/linux/compiler.h:243
IP: [< inline >] atomic_read arch/x86/include/asm/atomic.h:26
IP: [< inline >] search_memslots include/linux/kvm_host.h:900
IP: [< inline >] __gfn_to_memslot include/linux/kvm_host.h:928
IP: [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
IP: [<ffffffff8105a299>] kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
PGD 3e90a067 [ 2974.428060] PUD 6dc08067

Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 20506 Comm: syz-executor Not tainted 4.9.0-rc4+ #49
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff880066c08040 task.stack: ffff8800665a8000
RIP: 0010:[<ffffffff8105a299>] [< inline >] __read_once_size
include/linux/compiler.h:243
RIP: 0010:[<ffffffff8105a299>] [< inline >] atomic_read
arch/x86/include/asm/atomic.h:26
RIP: 0010:[<ffffffff8105a299>] [< inline >] search_memslots
include/linux/kvm_host.h:900
RIP: 0010:[<ffffffff8105a299>] [< inline >] __gfn_to_memslot
include/linux/kvm_host.h:928
RIP: 0010:[<ffffffff8105a299>] [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
RIP: 0010:[<ffffffff8105a299>] [<ffffffff8105a299>]
kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
RSP: 0018:ffff8800665af730 EFLAGS: 00010246
RAX: 0000000000000003 RBX: 0000000000000004 RCX: ffffc90000b65000
RDX: 0000000000000000 RSI: ffff88006d85a3f0 RDI: ffffc900058fc000
RBP: ffff8800665af808 R08: ffffed000ccb5f36 R09: ffffed000ccb5f36
R10: ffffed000ccb5f35 R11: ffff8800665af9af R12: ffffffffffffff70
R13: ffff88006cf98420 R14: 0000000000000001 R15: 0000000000000003
FS: 00007f569fcf5700(0000) GS:ffff88006e300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc90005907408 CR3: 0000000069c4f000 CR4: 00000000000026e0
Stack:
1ffff1000ccb5ef0 ffff88006b1cc0c0 ffff8800665af750 ffffc90005907408
0000000000000001 ffff88006b1cc000 0000000000000001 0000000000001000
ffff88006d85a3f0 ffffc900058fc000 0000000041b58ab3 ffffffff837c394f
Call Trace:
[<ffffffff8112696d>] kvm_lapic_set_vapic_addr+0xed/0x140
arch/x86/kvm/lapic.c:2217
[<ffffffff810a77e4>] kvm_arch_vcpu_ioctl+0x224/0x3100 arch/x86/kvm/x86.c:3425
uhci_hcd 0000:00:01.2: BAR 4: can't reserve [io 0xc680-0xc69f]
kvm_vm_ioctl_assign_device: Could not get access to device regions
[<ffffffff810608b2>] kvm_vcpu_ioctl+0x1e2/0xdd0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2708
[< inline >] vfs_ioctl fs/ioctl.c:43
[<ffffffff816b03cc>] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679
uhci_hcd 0000:00:01.2: BAR 4: can't reserve [io 0xc680-0xc69f]
kvm_vm_ioctl_assign_device: Could not get access to device regions
[< inline >] SYSC_ioctl fs/ioctl.c:694
[<ffffffff816b130f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
[<ffffffff831f0dc1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
Code: 03 48 b8 00 00 00 00 00 fc ff df 0f b6 14 02 48 89 f8 83 e0 07
83 c0 03 38 d0 7c 08 84 d2 0f 85 59 06 00 00 48 8b bd 70 ff ff ff <48>
63 87 08 b4 00 00 4c 8d 6f 08 48 8d 14 80 48 8d 04 50 49 8d
RIP [< inline >] __read_once_size include/linux/compiler.h:243
RIP [< inline >] atomic_read arch/x86/include/asm/atomic.h:26
RIP [< inline >] search_memslots include/linux/kvm_host.h:900
RIP [< inline >] __gfn_to_memslot include/linux/kvm_host.h:928
RIP [< inline >] gfn_to_memslot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1227
RIP [<ffffffff8105a299>] kvm_gfn_to_hva_cache_init+0x239/0x9f0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1951
RSP <ffff8800665af730>
CR2: ffffc90005907408
---[ end trace 1382154a6662ad57 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
reboot: cpu_has_vmx: ecx=80a02021 1


Also I've seen crashed in __gfn_to_hva_many on similar programs:
BUG: unable to handle kernel paging request in __gfn_to_hva_many
(but I don't have full reports for these)

Unfortunately this is not reproducible.

On commit 015ed9433be2b476ec7e2e6a9a411a56e3b5b035 (Nov 11).

[Paolo Bonzini]

This is likely the same as "kvm: suspicious RCU usage/missed lock in
kvm_lapic_set_vapic_addr":

Call Trace:
[<ffffffff8112696d>] kvm_lapic_set_vapic_addr+0xed/0x140 arch/x86/kvm/lapic.c:2217
[<ffffffff810a77e4>] kvm_arch_vcpu_ioctl+0x224/0x3100 arch/x86/kvm/x86.c:3425
[<ffffffff810608b2>] kvm_vcpu_ioctl+0x1e2/0xdd0

Paolo