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: [email protected]
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Christian Borntraeger <[email protected]>
Signed-off-by: Thomas Huth <[email protected]>
---
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;
--
2.18.1
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: [email protected]
> Reviewed-by: David Hildenbrand <[email protected]>
> Reviewed-by: Christian Borntraeger <[email protected]>
> Signed-off-by: Thomas Huth <[email protected]>
Reviewed-by: Janosch Frank <[email protected]>
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: [email protected]
> Reviewed-by: David Hildenbrand <[email protected]>
> Reviewed-by: Christian Borntraeger <[email protected]>
> Signed-off-by: Thomas Huth <[email protected]>
> ---
> 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;
>