From 3edbcff9bfe2ed632e518b3cfe807d062cee8269 Mon Sep 17 00:00:00 2001 From: Carsten Otte Date: Tue, 12 May 2009 17:21:52 +0200 Subject: [PATCH] KVM: s390: Sanity check on validity intercept This patch adds a sanity check for the content of the guest prefix register content before faulting in the cpu lowcore that it refers to. The guest might end up in an endless loop where SIE complains about missing lowcore with incorrect content of the prefix register without this fix. Reported-by: Mijo Safradin Signed-off-by: Carsten Otte Signed-off-by: Christian Ehrhardt Signed-off-by: Avi Kivity --- arch/s390/kvm/intercept.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c index 9d19803111ba..98997ccba501 100644 --- a/arch/s390/kvm/intercept.c +++ b/arch/s390/kvm/intercept.c @@ -154,17 +154,25 @@ static int handle_stop(struct kvm_vcpu *vcpu) static int handle_validity(struct kvm_vcpu *vcpu) { int viwhy = vcpu->arch.sie_block->ipb >> 16; + int rc; + vcpu->stat.exit_validity++; - if (viwhy == 0x37) { - fault_in_pages_writeable((char __user *) - vcpu->kvm->arch.guest_origin + - vcpu->arch.sie_block->prefix, - PAGE_SIZE); - return 0; - } - VCPU_EVENT(vcpu, 2, "unhandled validity intercept code %d", - viwhy); - return -ENOTSUPP; + if ((viwhy == 0x37) && (vcpu->arch.sie_block->prefix + <= vcpu->kvm->arch.guest_memsize - 2*PAGE_SIZE)){ + rc = fault_in_pages_writeable((char __user *) + vcpu->kvm->arch.guest_origin + + vcpu->arch.sie_block->prefix, + 2*PAGE_SIZE); + if (rc) + /* user will receive sigsegv, exit to user */ + rc = -ENOTSUPP; + } else + rc = -ENOTSUPP; + + if (rc) + VCPU_EVENT(vcpu, 2, "unhandled validity intercept code %d", + viwhy); + return rc; } static int handle_instruction(struct kvm_vcpu *vcpu) -- 2.34.1