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authorThomas Huth <thuth@redhat.com>2019-09-12 13:54:38 +0200
committerChristian Borntraeger <borntraeger@de.ibm.com>2019-09-12 14:12:21 +0200
commit53936b5bf35e140ae27e4bbf0447a61063f400da (patch)
parent13a17cc0526f08d1df9507f7484176371cd263a0 (diff)
KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl
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> Reviewed-by: Janosch Frank <frankja@linux.ibm.com> Signed-off-by: Thomas Huth <thuth@redhat.com> Link: https://lore.kernel.org/kvm/20190912115438.25761-1-thuth@redhat.com Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
2 files changed, 11 insertions, 1 deletions
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index b5fd6e85657c..d1ccc168c071 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1961,6 +1961,16 @@ int s390int_to_s390irq(struct kvm_s390_interrupt *s390int,
case KVM_S390_MCHK:
irq->u.mchk.mcic = s390int->parm64;
+ irq->u.ext.ext_params = s390int->parm;
+ irq->u.ext.ext_params2 = s390int->parm64;
+ break;
+ case KVM_S390_RESTART:
+ 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 b298fcc9ec56..0d697b436f2b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4335,7 +4335,7 @@ 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;