KVM: s390: ucontrol: Fix memslot handling

Fix memslots handling for UCONTROL guests. Attempts to delete user
memslots will fail, as they should, without the risk of a NULL pointer
dereference.

Fixes: 413c98f24c63 ("KVM: s390: fake memslot for ucontrol VMs")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 156878c95e06792cf307441137d88fb6f5dd3dae..63bc496d0c37e8bfe0aa54453a60f96f9a458913 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5642,7 +5642,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                                   struct kvm_memory_slot *new,
                                   enum kvm_mr_change change)
 {
-       if (kvm_is_ucontrol(kvm) && new->id < KVM_USER_MEM_SLOTS)
+       if (kvm_is_ucontrol(kvm) && new && new->id < KVM_USER_MEM_SLOTS)
                return -EINVAL;
 
        /* When we are protected, we should not change the memory slots */