[PATCH] KVM: s390: Check kvm pointer when testing KVM_CAP_S390_HPAGE_1M

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

KVM allows issuing the KVM_CHECK_EXTENSION ioctl either on the /dev/kvm
fd or the VM fd. In the first case, kvm_vm_ioctl_check_extension() is
called with kvm==NULL. Ensure we don't dereference the pointer in that
case.

Fixes: 40ebdb8e59df ("KVM: s390: Make huge pages unavailable in ucontrol VMs")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
Only build-tested
---
 arch/s390/kvm/kvm-s390.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 5147b943a864a..7721eb522f43d 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -587,7 +587,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 	case KVM_CAP_S390_HPAGE_1M:
 		r = 0;
-		if (hpage && !kvm_is_ucontrol(kvm))
+		if (hpage && !(kvm && kvm_is_ucontrol(kvm)))
 			r = 1;
 		break;
 	case KVM_CAP_S390_MEM_OP:
-- 
2.44.0