how to report kvm bug?

how to report kvm bug?

[Moguofang (Dennis mo)]

Hello!
         I found an out-of-bounds read bug in kvm kernel pio functions, how to report the bug?

Kind regards
moguofang

Re: how to report kvm bug?

[Wanpeng Li]

2017-05-18 14:51 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> Hello!
>          I found an out-of-bounds read bug in kvm kernel pio functions, how to report the bug?

You can post it here.

Regards,
Wanpeng Li

Re: 答复: how to report kvm bug?

[Wanpeng Li]

2017-05-18 15:25 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>
>
> -----邮件原件-----
> 发件人: Wanpeng Li [mailto:kernellwp@gmail.com]
> 发送时间: 2017年5月18日 15:19
> 收件人: Moguofang (Dennis mo)
> 抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
> 主题: Re: how to report kvm bug?
>
> 2017-05-18 14:51 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>> Hello!
>>          I found an out-of-bounds read bug in kvm kernel pio functions, how to report the bug?
>

I just figure it out and will send out a patch soon.

Regards,
Wanpeng Li

答复: 答复: how to report kvm bug?

[Moguofang (Dennis mo)]

Will you still need the C program or not? When the patch release?

-----邮件原件-----
发件人: Wanpeng Li [mailto:kernellwp@gmail.com] 
发送时间: 2017年5月18日 18:49
收件人: Moguofang (Dennis mo)
抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
主题: Re: 答复: how to report kvm bug?

2017-05-18 15:25 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>
>
> -----邮件原件-----
> 发件人: Wanpeng Li [mailto:kernellwp@gmail.com]
> 发送时间: 2017年5月18日 15:19
> 收件人: Moguofang (Dennis mo)
> 抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
> 主题: Re: how to report kvm bug?
>
> 2017-05-18 14:51 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>> Hello!
>>          I found an out-of-bounds read bug in kvm kernel pio functions, how to report the bug?
>

I just figure it out and will send out a patch soon.

Regards,
Wanpeng Li

Re: 答复: 答复: how to report kvm bug?

[Wanpeng Li]

2017-05-19 9:33 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> Will you still need the C program or not? When the patch release?

I just send out the patch w/ a similar test cast, please have a try.

Regards,
Wanpeng Li

Re: KVM vulnerability report about cpuid instruction

[Wanpeng Li]

2017-06-07 15:09 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> Hello!
>         A new vulnerability discover by me.

Thanks for the report, I will have a look.

Regards,
Wanpeng Li

Re: KVM vulnerability report about cpuid instruction

[Wanpeng Li]

2017-06-07 15:09 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> Hello!
>         A new vulnerability discover by me.

Could you test something like this?

--------------------------->8-------------------------------------------------------------

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index a181ae7..b927a42 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -779,19 +779,20 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

 static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)
 {
+    int j = i, nent = vcpu->arch.cpuid_nent;
     struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
-    int j, nent = vcpu->arch.cpuid_nent;
+    struct kvm_cpuid_entry2 *ej;

     e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
     /* when no next entry is found, the current entry[i] is reselected */
-    for (j = i + 1; ; j = (j + 1) % nent) {
-        struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
-        if (ej->function == e->function) {
-            ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
-            return j;
-        }
-    }
-    return 0; /* silence gcc, even though control never reaches here */
+    do {
+        j = (j + 1) % nent;
+        ej = &vcpu->arch.cpuid_entries[j];
+    } while(ej->function != e->function);
+
+    ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
+
+    return j;
 }

 /* find an entry with matching function, matching index (if needed), and that

答复: KVM vulnerability report about cpuid instruction

[Moguofang (Dennis mo)]

the patch fixed the oob vulnerability when i = 79, but maybe the patch introduces an infinite loop, if i = 79, then j = 0, the do-while loop use cpuid_entries[0-78] to compare cpuid_entries[79], maybe fall into infinite loop.

Kind regards
moguofang

-----邮件原件-----
发件人: Wanpeng Li [mailto:kernellwp@gmail.com] 
发送时间: 2017年6月7日 16:32
收件人: Moguofang (Dennis mo)
抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
主题: Re: KVM vulnerability report about cpuid instruction

2017-06-07 15:09 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> Hello!
>         A new vulnerability discover by me.

Could you test something like this?

--------------------------->8-------------------------------------------
--------------------------->------------------

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a181ae7..b927a42 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -779,19 +779,20 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

 static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)  {
+    int j = i, nent = vcpu->arch.cpuid_nent;
     struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
-    int j, nent = vcpu->arch.cpuid_nent;
+    struct kvm_cpuid_entry2 *ej;

     e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
     /* when no next entry is found, the current entry[i] is reselected */
-    for (j = i + 1; ; j = (j + 1) % nent) {
-        struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
-        if (ej->function == e->function) {
-            ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
-            return j;
-        }
-    }
-    return 0; /* silence gcc, even though control never reaches here */
+    do {
+        j = (j + 1) % nent;
+        ej = &vcpu->arch.cpuid_entries[j];
+    } while(ej->function != e->function);
+
+    ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
+
+    return j;
 }

 /* find an entry with matching function, matching index (if needed), and that

Re: 答复: KVM vulnerability report about cpuid instruction

[Wanpeng Li]

2017-06-07 17:14 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
> the patch fixed the oob vulnerability when i = 79, but maybe the patch introduces an infinite loop, if i = 79, then j = 0, the do-while loop use cpuid_entries[0-78] to compare cpuid_entries[79], maybe fall into infinite loop.

It will not happen, if i == j, then ej->function == e->function and
for loop exit.

Anyway, another method is:

- for (j = i + 1; ; j = (j + 1) % nent) {
+ for (j = (i + 1) % nent; ; j = (j + 1) % nent) {

Regards,
Wanpeng Li

>
> Kind regards
> moguofang
>
> -----邮件原件-----
> 发件人: Wanpeng Li [mailto:kernellwp@gmail.com]
> 发送时间: 2017年6月7日 16:32
> 收件人: Moguofang (Dennis mo)
> 抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
> 主题: Re: KVM vulnerability report about cpuid instruction
>
> 2017-06-07 15:09 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>> Hello!
>>         A new vulnerability discover by me.
>
> Could you test something like this?
>
> --------------------------->8-------------------------------------------
> --------------------------->------------------
>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a181ae7..b927a42 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -779,19 +779,20 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
>
>  static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)  {
> +    int j = i, nent = vcpu->arch.cpuid_nent;
>      struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
> -    int j, nent = vcpu->arch.cpuid_nent;
> +    struct kvm_cpuid_entry2 *ej;
>
>      e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
>      /* when no next entry is found, the current entry[i] is reselected */
> -    for (j = i + 1; ; j = (j + 1) % nent) {
> -        struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
> -        if (ej->function == e->function) {
> -            ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
> -            return j;
> -        }
> -    }
> -    return 0; /* silence gcc, even though control never reaches here */
> +    do {
> +        j = (j + 1) % nent;
> +        ej = &vcpu->arch.cpuid_entries[j];
> +    } while(ej->function != e->function);
> +
> +    ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
> +
> +    return j;
>  }
>
>  /* find an entry with matching function, matching index (if needed), and that

Re: 答复: KVM vulnerability report about cpuid instruction

[Wanpeng Li]

2017-06-07 17:54 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>:
> 2017-06-07 17:14 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>> the patch fixed the oob vulnerability when i = 79, but maybe the patch introduces an infinite loop, if i = 79, then j = 0, the do-while loop use cpuid_entries[0-78] to compare cpuid_entries[79], maybe fall into infinite loop.
>
> It will not happen, if i == j, then ej->function == e->function and
> for loop exit.
>
> Anyway, another method is:
>
> - for (j = i + 1; ; j = (j + 1) % nent) {
> + for (j = (i + 1) % nent; ; j = (j + 1) % nent) {

Paolo, which one do you prefer?

Regards,
Wanpeng Li

>>
>> Kind regards
>> moguofang
>>
>> -----邮件原件-----
>> 发件人: Wanpeng Li [mailto:kernellwp@gmail.com]
>> 发送时间: 2017年6月7日 16:32
>> 收件人: Moguofang (Dennis mo)
>> 抄送: kvm@vger.kernel.org; Zhouyu (Axis Zhou, ICSL)
>> 主题: Re: KVM vulnerability report about cpuid instruction
>>
>> 2017-06-07 15:09 GMT+08:00 Moguofang (Dennis mo) <moguofang@huawei.com>:
>>> Hello!
>>>         A new vulnerability discover by me.
>>
>> Could you test something like this?
>>
>> --------------------------->8-------------------------------------------
>> --------------------------->------------------
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a181ae7..b927a42 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -779,19 +779,20 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
>>
>>  static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)  {
>> +    int j = i, nent = vcpu->arch.cpuid_nent;
>>      struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
>> -    int j, nent = vcpu->arch.cpuid_nent;
>> +    struct kvm_cpuid_entry2 *ej;
>>
>>      e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
>>      /* when no next entry is found, the current entry[i] is reselected */
>> -    for (j = i + 1; ; j = (j + 1) % nent) {
>> -        struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
>> -        if (ej->function == e->function) {
>> -            ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
>> -            return j;
>> -        }
>> -    }
>> -    return 0; /* silence gcc, even though control never reaches here */
>> +    do {
>> +        j = (j + 1) % nent;
>> +        ej = &vcpu->arch.cpuid_entries[j];
>> +    } while(ej->function != e->function);
>> +
>> +    ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
>> +
>> +    return j;
>>  }
>>
>>  /* find an entry with matching function, matching index (if needed), and that