[v2] KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl
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Message ID 20190912115438.25761-1-thuth@redhat.com
State New
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Series
  • [v2] KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl
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Commit Message

Thomas Huth Sept. 12, 2019, 11:54 a.m. UTC
When the userspace program runs the KVM_S390_INTERRUPT ioctl to inject
an interrupt, we convert them from the legacy struct kvm_s390_interrupt
to the new struct kvm_s390_irq via the s390int_to_s390irq() function.
However, this function does not take care of all types of interrupts
that we can inject into the guest later (see do_inject_vcpu()). Since we
do not clear out the s390irq values before calling s390int_to_s390irq(),
there is a chance that we copy random data from the kernel stack which
could be leaked to the userspace later.

Specifically, the problem exists with the KVM_S390_INT_PFAULT_INIT
interrupt: s390int_to_s390irq() does not handle it, and the function
__inject_pfault_init() later copies irq->u.ext which contains the
random kernel stack data. This data can then be leaked either to
the guest memory in __deliver_pfault_init(), or the userspace might
retrieve it directly with the KVM_S390_GET_IRQ_STATE ioctl.

Fix it by handling that interrupt type in s390int_to_s390irq(), too,
and by making sure that the s390irq struct is properly pre-initialized.
And while we're at it, make sure that s390int_to_s390irq() now
directly returns -EINVAL for unknown interrupt types, so that we
immediately get a proper error code in case we add more interrupt
types to do_inject_vcpu() without updating s390int_to_s390irq()
sometime in the future.

Cc: stable@vger.kernel.org
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 arch/s390/kvm/interrupt.c | 10 ++++++++++
 arch/s390/kvm/kvm-s390.c  |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

Comments

Janosch Frank Sept. 12, 2019, 12:07 p.m. UTC | #1
On 9/12/19 1:54 PM, Thomas Huth wrote:
> When the userspace program runs the KVM_S390_INTERRUPT ioctl to inject
> an interrupt, we convert them from the legacy struct kvm_s390_interrupt
> to the new struct kvm_s390_irq via the s390int_to_s390irq() function.
> However, this function does not take care of all types of interrupts
> that we can inject into the guest later (see do_inject_vcpu()). Since we
> do not clear out the s390irq values before calling s390int_to_s390irq(),
> there is a chance that we copy random data from the kernel stack which
> could be leaked to the userspace later.
> 
> Specifically, the problem exists with the KVM_S390_INT_PFAULT_INIT
> interrupt: s390int_to_s390irq() does not handle it, and the function
> __inject_pfault_init() later copies irq->u.ext which contains the
> random kernel stack data. This data can then be leaked either to
> the guest memory in __deliver_pfault_init(), or the userspace might
> retrieve it directly with the KVM_S390_GET_IRQ_STATE ioctl.
> 
> Fix it by handling that interrupt type in s390int_to_s390irq(), too,
> and by making sure that the s390irq struct is properly pre-initialized.
> And while we're at it, make sure that s390int_to_s390irq() now
> directly returns -EINVAL for unknown interrupt types, so that we
> immediately get a proper error code in case we add more interrupt
> types to do_inject_vcpu() without updating s390int_to_s390irq()
> sometime in the future.
> 
> Cc: stable@vger.kernel.org
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Christian Borntraeger Sept. 12, 2019, 12:14 p.m. UTC | #2
thanks, applied and queued for 5.3 (need to do some regression testing before
sending out)

On 12.09.19 13:54, Thomas Huth wrote:
> When the userspace program runs the KVM_S390_INTERRUPT ioctl to inject
> an interrupt, we convert them from the legacy struct kvm_s390_interrupt
> to the new struct kvm_s390_irq via the s390int_to_s390irq() function.
> However, this function does not take care of all types of interrupts
> that we can inject into the guest later (see do_inject_vcpu()). Since we
> do not clear out the s390irq values before calling s390int_to_s390irq(),
> there is a chance that we copy random data from the kernel stack which
> could be leaked to the userspace later.
> 
> Specifically, the problem exists with the KVM_S390_INT_PFAULT_INIT
> interrupt: s390int_to_s390irq() does not handle it, and the function
> __inject_pfault_init() later copies irq->u.ext which contains the
> random kernel stack data. This data can then be leaked either to
> the guest memory in __deliver_pfault_init(), or the userspace might
> retrieve it directly with the KVM_S390_GET_IRQ_STATE ioctl.
> 
> Fix it by handling that interrupt type in s390int_to_s390irq(), too,
> and by making sure that the s390irq struct is properly pre-initialized.
> And while we're at it, make sure that s390int_to_s390irq() now
> directly returns -EINVAL for unknown interrupt types, so that we
> immediately get a proper error code in case we add more interrupt
> types to do_inject_vcpu() without updating s390int_to_s390irq()
> sometime in the future.
> 
> Cc: stable@vger.kernel.org
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  arch/s390/kvm/interrupt.c | 10 ++++++++++
>  arch/s390/kvm/kvm-s390.c  |  2 +-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 3e7efdd9228a..165dea4c7f19 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1960,6 +1960,16 @@ int s390int_to_s390irq(struct kvm_s390_interrupt *s390int,
>  	case KVM_S390_MCHK:
>  		irq->u.mchk.mcic = s390int->parm64;
>  		break;
> +	case KVM_S390_INT_PFAULT_INIT:
> +		irq->u.ext.ext_params = s390int->parm;
> +		irq->u.ext.ext_params2 = s390int->parm64;
> +		break;
> +	case KVM_S390_RESTART:
> +	case KVM_S390_INT_CLOCK_COMP:
> +	case KVM_S390_INT_CPU_TIMER:
> +		break;
> +	default:
> +		return -EINVAL;
>  	}
>  	return 0;
>  }
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index f329dcb3f44c..082eac2abc88 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4323,7 +4323,7 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp,
>  	}
>  	case KVM_S390_INTERRUPT: {
>  		struct kvm_s390_interrupt s390int;
> -		struct kvm_s390_irq s390irq;
> +		struct kvm_s390_irq s390irq = {};
>  
>  		if (copy_from_user(&s390int, argp, sizeof(s390int)))
>  			return -EFAULT;
>

Patch
diff mbox series

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 3e7efdd9228a..165dea4c7f19 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1960,6 +1960,16 @@  int s390int_to_s390irq(struct kvm_s390_interrupt *s390int,
 	case KVM_S390_MCHK:
 		irq->u.mchk.mcic = s390int->parm64;
 		break;
+	case KVM_S390_INT_PFAULT_INIT:
+		irq->u.ext.ext_params = s390int->parm;
+		irq->u.ext.ext_params2 = s390int->parm64;
+		break;
+	case KVM_S390_RESTART:
+	case KVM_S390_INT_CLOCK_COMP:
+	case KVM_S390_INT_CPU_TIMER:
+		break;
+	default:
+		return -EINVAL;
 	}
 	return 0;
 }
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f329dcb3f44c..082eac2abc88 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4323,7 +4323,7 @@  long kvm_arch_vcpu_async_ioctl(struct file *filp,
 	}
 	case KVM_S390_INTERRUPT: {
 		struct kvm_s390_interrupt s390int;
-		struct kvm_s390_irq s390irq;
+		struct kvm_s390_irq s390irq = {};
 
 		if (copy_from_user(&s390int, argp, sizeof(s390int)))
 			return -EFAULT;