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authorDavid Hildenbrand <david@redhat.com>2017-03-23 18:24:19 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-08 09:53:32 +0200
commit42462d23e60b89a3c2f7d8d63f5f4e464ba77727 (patch)
tree0912022bfdba9c3d6f5a25c3fef0d0f6d7b2daae /virt
parent3a1246b46df5210164ee43d4c5c560d0dc9ed2ce (diff)
KVM: kvm_io_bus_unregister_dev() should never fail
commit 90db10434b163e46da413d34db8d0e77404cc645 upstream. No caller currently checks the return value of kvm_io_bus_unregister_dev(). This is evil, as all callers silently go on freeing their device. A stale reference will remain in the io_bus, getting at least used again, when the iobus gets teared down on kvm_destroy_vm() - leading to use after free errors. There is nothing the callers could do, except retrying over and over again. So let's simply remove the bus altogether, print an error and make sure no one can access this broken bus again (returning -ENOMEM on any attempt to access it). Fixes: e93f8a0f821e ("KVM: convert io_bus to SRCU") Reported-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/eventfd.c3
-rw-r--r--virt/kvm/kvm_main.c40
2 files changed, 25 insertions, 18 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 46dbc0a7dfc1..49001fa84ead 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -868,7 +868,8 @@ kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
continue;
kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
- kvm->buses[bus_idx]->ioeventfd_count--;
+ if (kvm->buses[bus_idx])
+ kvm->buses[bus_idx]->ioeventfd_count--;
ioeventfd_release(p);
ret = 0;
break;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1ac5b7be7282..cb092bd9965b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -655,7 +655,8 @@ static void kvm_destroy_vm(struct kvm *kvm)
spin_unlock(&kvm_lock);
kvm_free_irq_routing(kvm);
for (i = 0; i < KVM_NR_BUSES; i++) {
- kvm_io_bus_destroy(kvm->buses[i]);
+ if (kvm->buses[i])
+ kvm_io_bus_destroy(kvm->buses[i]);
kvm->buses[i] = NULL;
}
kvm_coalesced_mmio_free(kvm);
@@ -3273,6 +3274,8 @@ int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
};
bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
r = __kvm_io_bus_write(vcpu, bus, &range, val);
return r < 0 ? r : 0;
}
@@ -3290,6 +3293,8 @@ int kvm_io_bus_write_cookie(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx,
};
bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
/* First try the device referenced by cookie. */
if ((cookie >= 0) && (cookie < bus->dev_count) &&
@@ -3340,6 +3345,8 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
};
bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
r = __kvm_io_bus_read(vcpu, bus, &range, val);
return r < 0 ? r : 0;
}
@@ -3352,6 +3359,9 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
struct kvm_io_bus *new_bus, *bus;
bus = kvm->buses[bus_idx];
+ if (!bus)
+ return -ENOMEM;
+
/* exclude ioeventfd which is limited by maximum fd */
if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
return -ENOSPC;
@@ -3371,45 +3381,41 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
}
/* Caller must hold slots_lock. */
-int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
- struct kvm_io_device *dev)
+void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
+ struct kvm_io_device *dev)
{
- int i, r;
+ int i;
struct kvm_io_bus *new_bus, *bus;
bus = kvm->buses[bus_idx];
-
- /*
- * It's possible the bus being released before hand. If so,
- * we're done here.
- */
if (!bus)
- return 0;
+ return;
- r = -ENOENT;
for (i = 0; i < bus->dev_count; i++)
if (bus->range[i].dev == dev) {
- r = 0;
break;
}
- if (r)
- return r;
+ if (i == bus->dev_count)
+ return;
new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count - 1) *
sizeof(struct kvm_io_range)), GFP_KERNEL);
- if (!new_bus)
- return -ENOMEM;
+ if (!new_bus) {
+ pr_err("kvm: failed to shrink bus, removing it completely\n");
+ goto broken;
+ }
memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
new_bus->dev_count--;
memcpy(new_bus->range + i, bus->range + i + 1,
(new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+broken:
rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
synchronize_srcu_expedited(&kvm->srcu);
kfree(bus);
- return r;
+ return;
}
static struct notifier_block kvm_cpu_notifier = {