Re: KASAN: stack-out-of-bounds Read in write_mmio

[Wanpeng Li]

2017-12-09 19:39 GMT+08:00 Tianyu Lan <lantianyu1986@xxxxxxxxx>:
> 2017-12-09 17:15 GMT+08:00 syzbot
> <bot+b19026412c772c86fca485fc8342e3490da9c269@xxxxxxxxxxxxxxxxxxxxxxxxx>:
>> syzkaller has found reproducer for the following crash on
>> ad4dac17f9d563b9e34aab78a34293b10993e9b5
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>>
>>
>> kvm: KVM_SET_TSS_ADDR need to be called before entering vcpu
>> ==================================================================
>> BUG: KASAN: stack-out-of-bounds in write_mmio+0x560/0x600
>> arch/x86/kvm/x86.c:4669
>> Read of size 8 at addr ffff8801c4587220 by task syzkaller601256/3159
>>
>> CPU: 1 PID: 3159 Comm: syzkaller601256 Not tainted 4.15.0-rc2-next-20171208+
>> #63
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:17 [inline]
>>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>>  print_address_description+0x73/0x250 mm/kasan/report.c:252
>>  kasan_report_error mm/kasan/report.c:351 [inline]
>>  kasan_report+0x25b/0x340 mm/kasan/report.c:409
>>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
>>  write_mmio+0x560/0x600 arch/x86/kvm/x86.c:4669
>>  emulator_read_write_onepage+0x45a/0xea0 arch/x86/kvm/x86.c:4739
>>  emulator_read_write+0xe7/0x540 arch/x86/kvm/x86.c:4788
>>  emulator_write_emulated arch/x86/kvm/x86.c:4825 [inline]
>>  emulator_fix_hypercall+0x14d/0x1b0 arch/x86/kvm/x86.c:6349
>>  em_hypercall+0x5d/0x120 arch/x86/kvm/emulate.c:3705
>>  x86_emulate_insn+0x55d/0x3c20 arch/x86/kvm/emulate.c:5498
>>  x86_emulate_instruction+0x411/0x1ad0 arch/x86/kvm/x86.c:5756
>>  emulate_instruction arch/x86/include/asm/kvm_host.h:1177 [inline]
>>  handle_exception+0x3d5/0xa20 arch/x86/kvm/vmx.c:5921
>>  vmx_handle_exit+0x25d/0x1ce0 arch/x86/kvm/vmx.c:8887
>>  vcpu_enter_guest arch/x86/kvm/x86.c:7068 [inline]
>>  vcpu_run arch/x86/kvm/x86.c:7130 [inline]
>>  kvm_arch_vcpu_ioctl_run+0x1836/0x5be0 arch/x86/kvm/x86.c:7300
>>  kvm_vcpu_ioctl+0x64c/0x1010 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2555
>>  vfs_ioctl fs/ioctl.c:46 [inline]
>>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>>  SYSC_ioctl fs/ioctl.c:701 [inline]
>>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>> RIP: 0033:0x4435c9
>> RSP: 002b:00007fffdf34ced8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 00000000205b3000 RCX: 00000000004435c9
>> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
>> RBP: 000000000000000b R08: 0000000000000000 R09: 0000000000000002
>> R10: 0000000000000012 R11: 0000000000000202 R12: 00000000205b7e00
>> R13: 00000000205b6e00 R14: 00000000205b7a00 R15: 00000000205b3000
>>
>> The buggy address belongs to the page:
>> page:000000002e827842 count:0 mapcount:0 mapping:          (null) index:0x0
>> flags: 0x2fffc0000000000()
>> raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
>> raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff8801c4587100: f2 f2 f2 f2 00 f2 f2 f2 f3 f3 f3 f3 00 00 00 00
>>  ffff8801c4587180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>>
>>> ffff8801c4587200: f1 f1 f1 f1 03 f2 f2 f2 f3 f3 f3 f3 00 00 00 00
>>
>>                                ^
>>  ffff8801c4587280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>  ffff8801c4587300: 00 f1 f1 f1 f1 02 f2 f2 f2 f2 f2 f2 f2 00 f2 f2
>> ==================================================================
>>
>
> This issue seems to be as same as previous pop issue. I will have a look.

It is the *(u64 *)val in trace_kvm_mmio() causes the
stack-out-of-bounds, I will cook a patch soon.

Regards,
Wanpeng Li