| Message ID | 20190912115438.25761-1-thuth@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl | expand |
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>
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; >
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;