From 987d1149be7ddcc1380ff946cf236874421a7e1b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 17 Dec 2018 09:36:19 -0800 Subject: [PATCH] KVM: fix unregistering coalesced mmio zone from wrong bus 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: 0804c849f1df ("kvm/x86 : add coalesced pio support") Signed-off-by: Eric Biggers Signed-off-by: Paolo Bonzini --- virt/kvm/coalesced_mmio.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c index 3710342cf6ad..6855cce3e528 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -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);