[Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Paolo Bonzini]

---
 _posts/2018-01-04-spectre.md | 60 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 _posts/2018-01-04-spectre.md

diff --git a/_posts/2018-01-04-spectre.md b/_posts/2018-01-04-spectre.md
new file mode 100644
index 0000000..1be86d0
--- /dev/null
+++ b/_posts/2018-01-04-spectre.md
@@ -0,0 +1,60 @@
+---
+layout: post
+title:  "QEMU and the Spectre and Meltdown attacks"
+date:   2018-01-04 18:00:00 +0000
+author: Paolo Bonzini and Eduardo Habkost
+categories: [meltdown, spectre, security, x86]
+---
+As you probably know by now, three critical architectural flaws in CPUs have
+been recently disclosed that allow user processes to read kernel or hypervisor
+memory through cache side-channel attacks.  These flaws, collectively
+named _Meltdown_ and _Spectre_, affect in one way or another almost
+all processors that perform out-of-order execution, including x86 (from
+Intel and AMD), POWER, s390 and ARM processors.
+
+No microcode updates are required to block the _Meltdown_ attack; it is
+enough to update the guest operating system to a version that separates
+the user and kernel address spaces (known as _page table isolation_ for
+the Linux kernel).  Therefore, this post will focus on _Spectre_, and
+especially on [CVE-2017-5715](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715).
+
+Fixing or mitigating _Spectre_ in general, and CVE-2017-5715 in particular,
+requires cooperation between the processor and the operating system kernel or
+hypervisor; the processor can be updated through microcode or millicode
+patches to provide the required functionality.  CVE-2017-5715 allows guests
+to read potentially sensitive data from hypervisor memory; however, __patching
+the host kernel is sufficient to block this attack__.
+
+On the other hand, in order to protect the guest kernel from a malicious
+userspace, updates are also needed to the guest kernel and, depending on
+the processor architecture, to QEMU.  Just like on bare-metal, the guest
+kernel will use the new functionality provided by the microcode or millicode
+updates.  When running under a hypervisor, processor emulation is mostly out of
+QEMU's scope, so QEMU's role in the fix is small, but nevertheless important.
+In the case of KVM:
+
+* QEMU configures the hypervisor to emulate a specific processor model.
+For x86, QEMU has to be aware of new CPUID bits introduced by the microcode
+update, and it must provide them to guests depending on how the guest is
+configured.
+
+* upon virtual machine migration, QEMU reads the CPU state on the source
+and transmits it to the destination.  For x86, QEMU has to be aware of new
+model specific registers (MSRs).
+
+Right now, there are no public patches to KVM that expose the new CPUID bits
+and MSRs to the virtual machines, therefore there is no urgent need to update
+QEMU; remember that __updating the host kernel is enough to protect the
+host from malicious guests__.  Nevertheless, updates will be posted to the
+qemu-devel mailing list in the next few days, and a 2.11.1 patch release
+will be released with the fix.
+
+As of today, the QEMU project is not aware of whether similar changes will
+be required for non-x86 processors.  If so, they will also posted to the
+mailing list and backported to recent stable releases.
+
+For more information on the vulnerabilities, please refer to the [Google Security
+Blog](https://security.googleblog.com/2018/01/todays-cpu-vulnerability-what-you-need.html)
+and [Google Project
+Zero](https://googleprojectzero.blogspot.it/2018/01/reading-privileged-memory-with-side.html)
+posts on the topic, as well as the [Spectre and Meltdown FAQ](https://meltdownattack.com/#faq).
-- 
2.14.3

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Paolo Bonzini]

On 04/01/2018 18:56, Paolo Bonzini wrote:
> ---
>  _posts/2018-01-04-spectre.md | 60 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
>  create mode 100644 _posts/2018-01-04-spectre.md

Something on TCG ("it is not considered a security boundary, so it's
vulnerable to the CVE and no fix is planned") may be worth adding too.
It can be updated later.

Paolo

> diff --git a/_posts/2018-01-04-spectre.md b/_posts/2018-01-04-spectre.md
> new file mode 100644
> index 0000000..1be86d0
> --- /dev/null
> +++ b/_posts/2018-01-04-spectre.md
> @@ -0,0 +1,60 @@
> +---
> +layout: post
> +title:  "QEMU and the Spectre and Meltdown attacks"
> +date:   2018-01-04 18:00:00 +0000
> +author: Paolo Bonzini and Eduardo Habkost
> +categories: [meltdown, spectre, security, x86]
> +---
> +As you probably know by now, three critical architectural flaws in CPUs have
> +been recently disclosed that allow user processes to read kernel or hypervisor
> +memory through cache side-channel attacks.  These flaws, collectively
> +named _Meltdown_ and _Spectre_, affect in one way or another almost
> +all processors that perform out-of-order execution, including x86 (from
> +Intel and AMD), POWER, s390 and ARM processors.
> +
> +No microcode updates are required to block the _Meltdown_ attack; it is
> +enough to update the guest operating system to a version that separates
> +the user and kernel address spaces (known as _page table isolation_ for
> +the Linux kernel).  Therefore, this post will focus on _Spectre_, and
> +especially on [CVE-2017-5715](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715).
> +
> +Fixing or mitigating _Spectre_ in general, and CVE-2017-5715 in particular,
> +requires cooperation between the processor and the operating system kernel or
> +hypervisor; the processor can be updated through microcode or millicode
> +patches to provide the required functionality.  CVE-2017-5715 allows guests
> +to read potentially sensitive data from hypervisor memory; however, __patching
> +the host kernel is sufficient to block this attack__.
> +
> +On the other hand, in order to protect the guest kernel from a malicious
> +userspace, updates are also needed to the guest kernel and, depending on
> +the processor architecture, to QEMU.  Just like on bare-metal, the guest
> +kernel will use the new functionality provided by the microcode or millicode
> +updates.  When running under a hypervisor, processor emulation is mostly out of
> +QEMU's scope, so QEMU's role in the fix is small, but nevertheless important.
> +In the case of KVM:
> +
> +* QEMU configures the hypervisor to emulate a specific processor model.
> +For x86, QEMU has to be aware of new CPUID bits introduced by the microcode
> +update, and it must provide them to guests depending on how the guest is
> +configured.
> +
> +* upon virtual machine migration, QEMU reads the CPU state on the source
> +and transmits it to the destination.  For x86, QEMU has to be aware of new
> +model specific registers (MSRs).
> +
> +Right now, there are no public patches to KVM that expose the new CPUID bits
> +and MSRs to the virtual machines, therefore there is no urgent need to update
> +QEMU; remember that __updating the host kernel is enough to protect the
> +host from malicious guests__.  Nevertheless, updates will be posted to the
> +qemu-devel mailing list in the next few days, and a 2.11.1 patch release
> +will be released with the fix.
> +
> +As of today, the QEMU project is not aware of whether similar changes will
> +be required for non-x86 processors.  If so, they will also posted to the
> +mailing list and backported to recent stable releases.
> +
> +For more information on the vulnerabilities, please refer to the [Google Security
> +Blog](https://security.googleblog.com/2018/01/todays-cpu-vulnerability-what-you-need.html)
> +and [Google Project
> +Zero](https://googleprojectzero.blogspot.it/2018/01/reading-privileged-memory-with-side.html)
> +posts on the topic, as well as the [Spectre and Meltdown FAQ](https://meltdownattack.com/#faq).
> 

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Eduardo Habkost]

On Thu, Jan 04, 2018 at 06:56:09PM +0100, Paolo Bonzini wrote:
> ---
>  _posts/2018-01-04-spectre.md | 60 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
>  create mode 100644 _posts/2018-01-04-spectre.md

Thanks for writing it up!

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

> 
> diff --git a/_posts/2018-01-04-spectre.md b/_posts/2018-01-04-spectre.md
> new file mode 100644
> index 0000000..1be86d0
> --- /dev/null
> +++ b/_posts/2018-01-04-spectre.md
> @@ -0,0 +1,60 @@
> +---
> +layout: post
> +title:  "QEMU and the Spectre and Meltdown attacks"
> +date:   2018-01-04 18:00:00 +0000
> +author: Paolo Bonzini and Eduardo Habkost
> +categories: [meltdown, spectre, security, x86]
> +---
> +As you probably know by now, three critical architectural flaws in CPUs have
> +been recently disclosed that allow user processes to read kernel or hypervisor
> +memory through cache side-channel attacks.  These flaws, collectively
> +named _Meltdown_ and _Spectre_, affect in one way or another almost
> +all processors that perform out-of-order execution, including x86 (from
> +Intel and AMD), POWER, s390 and ARM processors.
> +
> +No microcode updates are required to block the _Meltdown_ attack; it is
> +enough to update the guest operating system to a version that separates
> +the user and kernel address spaces (known as _page table isolation_ for
> +the Linux kernel).  Therefore, this post will focus on _Spectre_, and
> +especially on [CVE-2017-5715](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715).
> +
> +Fixing or mitigating _Spectre_ in general, and CVE-2017-5715 in particular,
> +requires cooperation between the processor and the operating system kernel or
> +hypervisor; the processor can be updated through microcode or millicode
> +patches to provide the required functionality.  CVE-2017-5715 allows guests
> +to read potentially sensitive data from hypervisor memory; however, __patching
> +the host kernel is sufficient to block this attack__.
> +
> +On the other hand, in order to protect the guest kernel from a malicious
> +userspace, updates are also needed to the guest kernel and, depending on
> +the processor architecture, to QEMU.  Just like on bare-metal, the guest
> +kernel will use the new functionality provided by the microcode or millicode
> +updates.  When running under a hypervisor, processor emulation is mostly out of
> +QEMU's scope, so QEMU's role in the fix is small, but nevertheless important.
> +In the case of KVM:
> +
> +* QEMU configures the hypervisor to emulate a specific processor model.
> +For x86, QEMU has to be aware of new CPUID bits introduced by the microcode
> +update, and it must provide them to guests depending on how the guest is
> +configured.
> +
> +* upon virtual machine migration, QEMU reads the CPU state on the source
> +and transmits it to the destination.  For x86, QEMU has to be aware of new
> +model specific registers (MSRs).
> +
> +Right now, there are no public patches to KVM that expose the new CPUID bits
> +and MSRs to the virtual machines, therefore there is no urgent need to update
> +QEMU; remember that __updating the host kernel is enough to protect the
> +host from malicious guests__.  Nevertheless, updates will be posted to the
> +qemu-devel mailing list in the next few days, and a 2.11.1 patch release
> +will be released with the fix.
> +
> +As of today, the QEMU project is not aware of whether similar changes will
> +be required for non-x86 processors.  If so, they will also posted to the
> +mailing list and backported to recent stable releases.
> +
> +For more information on the vulnerabilities, please refer to the [Google Security
> +Blog](https://security.googleblog.com/2018/01/todays-cpu-vulnerability-what-you-need.html)
> +and [Google Project
> +Zero](https://googleprojectzero.blogspot.it/2018/01/reading-privileged-memory-with-side.html)
> +posts on the topic, as well as the [Spectre and Meltdown FAQ](https://meltdownattack.com/#faq).
> -- 
> 2.14.3
> 

-- 
Eduardo

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Alexandre DERUMIER]

Thanks Paolo !

Do we need to update guest kernel too, if qemu use cpumodel=qemu64 ?

(For example,  I have some very old guests where kernel update is not possible)

Regards,

Alexandre

----- Mail original -----
De: "pbonzini" <pbonzini@redhat.com>
À: "qemu-devel" <qemu-devel@nongnu.org>
Cc: "ehabkost" <ehabkost@redhat.com>
Envoyé: Jeudi 4 Janvier 2018 18:56:09
Objet: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

--- 
_posts/2018-01-04-spectre.md | 60 ++++++++++++++++++++++++++++++++++++++++++++ 
1 file changed, 60 insertions(+) 
create mode 100644 _posts/2018-01-04-spectre.md 

diff --git a/_posts/2018-01-04-spectre.md b/_posts/2018-01-04-spectre.md 
new file mode 100644 
index 0000000..1be86d0 
--- /dev/null 
+++ b/_posts/2018-01-04-spectre.md 
@@ -0,0 +1,60 @@ 
+--- 
+layout: post 
+title: "QEMU and the Spectre and Meltdown attacks" 
+date: 2018-01-04 18:00:00 +0000 
+author: Paolo Bonzini and Eduardo Habkost 
+categories: [meltdown, spectre, security, x86] 
+--- 
+As you probably know by now, three critical architectural flaws in CPUs have 
+been recently disclosed that allow user processes to read kernel or hypervisor 
+memory through cache side-channel attacks. These flaws, collectively 
+named _Meltdown_ and _Spectre_, affect in one way or another almost 
+all processors that perform out-of-order execution, including x86 (from 
+Intel and AMD), POWER, s390 and ARM processors. 
+ 
+No microcode updates are required to block the _Meltdown_ attack; it is 
+enough to update the guest operating system to a version that separates 
+the user and kernel address spaces (known as _page table isolation_ for 
+the Linux kernel). Therefore, this post will focus on _Spectre_, and 
+especially on [CVE-2017-5715](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715). 
+ 
+Fixing or mitigating _Spectre_ in general, and CVE-2017-5715 in particular, 
+requires cooperation between the processor and the operating system kernel or 
+hypervisor; the processor can be updated through microcode or millicode 
+patches to provide the required functionality. CVE-2017-5715 allows guests 
+to read potentially sensitive data from hypervisor memory; however, __patching 
+the host kernel is sufficient to block this attack__. 
+ 
+On the other hand, in order to protect the guest kernel from a malicious 
+userspace, updates are also needed to the guest kernel and, depending on 
+the processor architecture, to QEMU. Just like on bare-metal, the guest 
+kernel will use the new functionality provided by the microcode or millicode 
+updates. When running under a hypervisor, processor emulation is mostly out of 
+QEMU's scope, so QEMU's role in the fix is small, but nevertheless important. 
+In the case of KVM: 
+ 
+* QEMU configures the hypervisor to emulate a specific processor model. 
+For x86, QEMU has to be aware of new CPUID bits introduced by the microcode 
+update, and it must provide them to guests depending on how the guest is 
+configured. 
+ 
+* upon virtual machine migration, QEMU reads the CPU state on the source 
+and transmits it to the destination. For x86, QEMU has to be aware of new 
+model specific registers (MSRs). 
+ 
+Right now, there are no public patches to KVM that expose the new CPUID bits 
+and MSRs to the virtual machines, therefore there is no urgent need to update 
+QEMU; remember that __updating the host kernel is enough to protect the 
+host from malicious guests__. Nevertheless, updates will be posted to the 
+qemu-devel mailing list in the next few days, and a 2.11.1 patch release 
+will be released with the fix. 
+ 
+As of today, the QEMU project is not aware of whether similar changes will 
+be required for non-x86 processors. If so, they will also posted to the 
+mailing list and backported to recent stable releases. 
+ 
+For more information on the vulnerabilities, please refer to the [Google Security 
+Blog](https://security.googleblog.com/2018/01/todays-cpu-vulnerability-what-you-need.html) 
+and [Google Project 
+Zero](https://googleprojectzero.blogspot.it/2018/01/reading-privileged-memory-with-side.html) 
+posts on the topic, as well as the [Spectre and Meltdown FAQ](https://meltdownattack.com/#faq). 
-- 
2.14.3 

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Paolo Bonzini]

On 04/01/2018 19:13, Alexandre DERUMIER wrote:
> Thanks Paolo !
> 
> Do we need to update guest kernel too, if qemu use cpumodel=qemu64 ?
> 
> (For example,  I have some very old guests where kernel update is not possible)

If you want to be protected against the other two CVEs (one of which is
"Meltdown"), yes.

Paolo

> Regards,
> 
> Alexandre

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Stefan Hajnoczi]

Thanks Paolo and Eduardo.  I have posted the link on QEMU's Google+ page.

Stefan

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Fam Zheng]

On Thu, 01/04 18:56, Paolo Bonzini wrote:
> +be required for non-x86 processors.  If so, they will also posted to the

Hi Paolo, they will also "be" posted?

Fam

Re: [Qemu-devel] [qemu-web PATCH] add a blog post about "Spectre"

[Paolo Bonzini]

On 09/01/2018 03:13, Fam Zheng wrote:
> On Thu, 01/04 18:56, Paolo Bonzini wrote:
>> +be required for non-x86 processors.  If so, they will also posted to the
> 
> Hi Paolo, they will also "be" posted?

Thanks!  Pushed the small fix.

Paolo