From 6687863c4e45b4f6bf2a65d9eece23f494c1b06f Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 6 Mar 2018 14:27:58 +0100 Subject: KVM: s390: fix memory overwrites when not using SCA entries commit f07afa0462b76a5b9c4f3a43d5ac24fdb86a90c2 upstream. Even if we don't have extended SCA support, we can have more than 64 CPUs if we don't enable any HW features that might use the SCA entries. Now, this works just fine, but we missed a return, which is why we would actually store the SCA entries. If we have more than 64 CPUs, this means writing outside of the basic SCA - bad. Let's fix this. This allows > 64 CPUs when running nested (under vSIE) without random crashes. Fixes: a6940674c384 ("KVM: s390: allow 255 VCPUs when sca entries aren't used") Reported-by: Christian Borntraeger Tested-by: Christian Borntraeger Signed-off-by: David Hildenbrand Message-Id: <20180306132758.21034-1-david@redhat.com> Cc: stable@vger.kernel.org Reviewed-by: Cornelia Huck Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman --- arch/s390/kvm/kvm-s390.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch') diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 5ba494ed18c1..a70ff09b4982 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1601,6 +1601,7 @@ static void sca_add_vcpu(struct kvm_vcpu *vcpu) /* we still need the basic sca for the ipte control */ vcpu->arch.sie_block->scaoh = (__u32)(((__u64)sca) >> 32); vcpu->arch.sie_block->scaol = (__u32)(__u64)sca; + return; } read_lock(&vcpu->kvm->arch.sca_lock); if (vcpu->kvm->arch.use_esca) { -- cgit v1.2.3