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KVM: fix unregistering coalesced mmio zone from wrong bus

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If you register a kvm_coalesced_mmio_zone with '.pio = 0' but then
unregister it with '.pio = 1', KVM_UNREGISTER_COALESCED_MMIO will try to
unregister it from KVM_PIO_BUS rather than KVM_MMIO_BUS, which is a
no-op.  But it frees the kvm_coalesced_mmio_dev anyway, causing a
use-after-free.

Fix it by only unregistering and freeing the zone if the correct value
of 'pio' is provided.

Reported-by: syzbot+f87f60bb6f13f39b54e3@syzkaller.appspotmail.com
Fixes: 0804c849f1 ("kvm/x86 : add coalesced pio support")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eric Biggers 2018-12-17 09:36:19 -08:00 committed by Paolo Bonzini
parent 7566ec393f
commit 987d1149be
1 changed files with 5 additions and 1 deletions
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6
virt/kvm/coalesced_mmio.c
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@ -175,10 +175,14 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
{
struct kvm_coalesced_mmio_dev *dev, *tmp;
if (zone->pio != 1 && zone->pio != 0)
return -EINVAL;
mutex_lock(&kvm->slots_lock);
list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
if (zone->pio == dev->zone.pio &&
coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
kvm_io_bus_unregister_dev(kvm,
zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
kvm_iodevice_destructor(&dev->dev);