[PATCH] kvm: Initialize all struct members to avoid stack information leak

[PATCH] kvm: Initialize all struct members to avoid stack information leak

[Marcus Meissner]

Hi,

Reported to us by Stephan Mueller of atsec.

Several .pad struct members are not set to something, so they
will leak stack content back to user space.

Ciao, Marcus

Reported-by: Stephan Mueller <smueller@atsec.com>
Signed-off-by: Marcus Meissner <meissner@suse.de>
---
 arch/x86/kvm/x86.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 77c9d86..621ffb6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3002,6 +3002,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	case KVM_GET_VCPU_EVENTS: {
 		struct kvm_vcpu_events events;
 
+		memset(&events, 0, sizeof(events));
 		kvm_vcpu_ioctl_x86_get_vcpu_events(vcpu, &events);
 
 		r = -EFAULT;
-- 
1.7.6

Re: [PATCH] kvm: Initialize all struct members to avoid stack information leak

[Juan Quintela]

Marcus Meissner <meissner@novell.com> wrote:
> Hi,
>
> Reported to us by Stephan Mueller of atsec.
>
> Several .pad struct members are not set to something, so they
> will leak stack content back to user space.
>
> Ciao, Marcus
>
> Reported-by: Stephan Mueller <smueller@atsec.com>
> Signed-off-by: Marcus Meissner <meissner@suse.de>
> ---
>  arch/x86/kvm/x86.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 77c9d86..621ffb6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3002,6 +3002,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  	case KVM_GET_VCPU_EVENTS: {
>  		struct kvm_vcpu_events events;
>  
> +		memset(&events, 0, sizeof(events));
>  		kvm_vcpu_ioctl_x86_get_vcpu_events(vcpu, &events);
>  
>  		r = -EFAULT;

Looking at arch/x86/include/asm/kvm.h & arch/x86/kvm/x86.c I can't see
what pad fields are not initialized.  My reading is that everything is
initialized in kvm_vcpu_ioctl_x86_get_vcpu_events().  What field are you
refering to?

Later, Juan.

Re: [PATCH] kvm: Initialize all struct members to avoid stack information leak

[Jan Kiszka]

On 2011-07-19 16:12, Juan Quintela wrote:
> Marcus Meissner <meissner@novell.com> wrote:
>> Hi,
>>
>> Reported to us by Stephan Mueller of atsec.
>>
>> Several .pad struct members are not set to something, so they
>> will leak stack content back to user space.
>>
>> Ciao, Marcus
>>
>> Reported-by: Stephan Mueller <smueller@atsec.com>
>> Signed-off-by: Marcus Meissner <meissner@suse.de>
>> ---
>>  arch/x86/kvm/x86.c |    1 +
>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 77c9d86..621ffb6 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -3002,6 +3002,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>  	case KVM_GET_VCPU_EVENTS: {
>>  		struct kvm_vcpu_events events;
>>  
>> +		memset(&events, 0, sizeof(events));
>>  		kvm_vcpu_ioctl_x86_get_vcpu_events(vcpu, &events);
>>  
>>  		r = -EFAULT;
> 
> Looking at arch/x86/include/asm/kvm.h & arch/x86/kvm/x86.c I can't see
> what pad fields are not initialized.  My reading is that everything is
> initialized in kvm_vcpu_ioctl_x86_get_vcpu_events().  What field are you
> refering to?

Good question. Information leaks were once addressed by 97e69aa62f, and
kvm_vcpu_events was not changed since then.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux

Re: [PATCH] kvm: Initialize all struct members to avoid stack information leak

[Marcus Meissner]

On Tue, Jul 19, 2011 at 07:38:27PM +0200, Jan Kiszka wrote:
> On 2011-07-19 16:12, Juan Quintela wrote:
> > Marcus Meissner <meissner@novell.com> wrote:
> >> Hi,
> >>
> >> Reported to us by Stephan Mueller of atsec.
> >>
> >> Several .pad struct members are not set to something, so they
> >> will leak stack content back to user space.
> >>
> >> Ciao, Marcus
> >>
> >> Reported-by: Stephan Mueller <smueller@atsec.com>
> >> Signed-off-by: Marcus Meissner <meissner@suse.de>
> >> ---
> >>  arch/x86/kvm/x86.c |    1 +
> >>  1 files changed, 1 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index 77c9d86..621ffb6 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -3002,6 +3002,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> >>  	case KVM_GET_VCPU_EVENTS: {
> >>  		struct kvm_vcpu_events events;
> >>  
> >> +		memset(&events, 0, sizeof(events));
> >>  		kvm_vcpu_ioctl_x86_get_vcpu_events(vcpu, &events);
> >>  
> >>  		r = -EFAULT;
> > 
> > Looking at arch/x86/include/asm/kvm.h & arch/x86/kvm/x86.c I can't see
> > what pad fields are not initialized.  My reading is that everything is
> > initialized in kvm_vcpu_ioctl_x86_get_vcpu_events().  What field are you
> > refering to?
> 
> Good question. Information leaks were once addressed by 97e69aa62f, and
> kvm_vcpu_events was not changed since then.

I was looking at old code, did not cross check if it is fixed in mainline.

Sorry for the noise.

Ciao, Marcus