From: David Hildenbrand Date: Tue, 6 Mar 2018 13:27:58 +0000 (+0100) Subject: KVM: s390: fix memory overwrites when not using SCA entries X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f07afa0462b76a5b9c4f3a43d5ac24fdb86a90c2;p=linux.git KVM: s390: fix memory overwrites when not using SCA entries 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 --- diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index df19f158347e0..339ac0964590a 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2147,6 +2147,7 @@ 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) {