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authorDavid Hildenbrand <david@redhat.com>2017-03-23 18:24:19 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-22 07:15:03 +0200
commit07882feab469f30e8e67b6aa02e2913004dac1da (patch)
tree25380e6592f705f6b1268c8d0be8268d714692be /virt
parentc6216a0f1e3da39f37aba3d43257c8cda172b414 (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 5a310caf4bbe..64238c9c5dce 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -866,7 +866,8 @@ 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 5f7bff5b9e4e..3d5ae6f655df 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -615,7 +615,8 @@ 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);
@@ -2980,6 +2981,8 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
};
bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
r = __kvm_io_bus_write(bus, &range, val);
return r < 0 ? r : 0;
}
@@ -2997,6 +3000,8 @@ int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
};
bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
/* First try the device referenced by cookie. */
if ((cookie >= 0) && (cookie < bus->dev_count) &&
@@ -3047,6 +3052,8 @@ int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
};
bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+ if (!bus)
+ return -ENOMEM;
r = __kvm_io_bus_read(bus, &range, val);
return r < 0 ? r : 0;
}
@@ -3059,6 +3066,9 @@ 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;
@@ -3078,45 +3088,41 @@ 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 = kzalloc(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 = {