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KVM: s390: Sanity check on validity intercept

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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 <mijo@linux.vnet.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Carsten Otte 2009-05-12 17:21:52 +02:00 committed by Avi Kivity
parent abf4a71ed9
commit 3edbcff9bf
1 changed files with 18 additions and 10 deletions
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28
arch/s390/kvm/intercept.c
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@ -154,17 +154,25 @@ static int handle_stop(struct kvm_vcpu *vcpu)
static int handle_validity(struct kvm_vcpu *vcpu) static int handle_validity(struct kvm_vcpu *vcpu)
{ {
int viwhy = vcpu->arch.sie_block->ipb >> 16; int viwhy = vcpu->arch.sie_block->ipb >> 16;
int rc;
vcpu->stat.exit_validity++; vcpu->stat.exit_validity++;
if (viwhy == 0x37) { if ((viwhy == 0x37) && (vcpu->arch.sie_block->prefix
fault_in_pages_writeable((char __user *) <= vcpu->kvm->arch.guest_memsize - 2*PAGE_SIZE)){
vcpu->kvm->arch.guest_origin + rc = fault_in_pages_writeable((char __user *)
vcpu->arch.sie_block->prefix, vcpu->kvm->arch.guest_origin +
PAGE_SIZE); vcpu->arch.sie_block->prefix,
return 0; 2*PAGE_SIZE);
} if (rc)
VCPU_EVENT(vcpu, 2, "unhandled validity intercept code %d", /* user will receive sigsegv, exit to user */
viwhy); rc = -ENOTSUPP;
return -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) static int handle_instruction(struct kvm_vcpu *vcpu)