KVM: s390: Disable dirty log retrieval for UCONTROL guests

User controlled KVM guests do not support the dirty log, as they have
no single gmap that we can check for changes.

As they have no single gmap, kvm->arch.gmap is NULL and all further
referencing to it for dirty checking will result in a NULL
dereference.

Let's return -EINVAL if a caller tries to sync dirty logs for a
UCONTROL guest.

Fixes: 15f36eb ("KVM: s390: Add proper dirty bitmap support to S390 kvm.")
Cc: <stable@vger.kernel.org> # 3.16+
Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index dabd3b15bf11b8d66cf26a6ccaebe650bff70dcd..502de74ea984b4d56ccb935f1f042cb593066692 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -442,6 +442,9 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
        struct kvm_memory_slot *memslot;
        int is_dirty = 0;
 
+       if (kvm_is_ucontrol(kvm))
+               return -EINVAL;
+
        mutex_lock(&kvm->slots_lock);
 
        r = -EINVAL;