If allocating a new instance of an I/O bus fails when unregistering a
device, wait to destroy the device until after all readers are guaranteed
to see the new null bus. Destroying devices before the bus is nullified
could lead to use-after-free since readers expect the devices on their
reference of the bus to remain valid.
Fixes: f65886606c2d ("KVM: fix memory leak in kvm_io_bus_unregister_dev()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
virt/kvm/kvm_main.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 383df23514b9..d6e2b570e430 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4511,7 +4511,13 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
new_bus->dev_count--;
memcpy(new_bus->range + i, bus->range + i + 1,
flex_array_size(new_bus, range, new_bus->dev_count - i));
- } else {
+ }
+
+ rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
+ synchronize_srcu_expedited(&kvm->srcu);
+
+ /* Destroy the old bus _after_ installing the (null) bus. */
+ if (!new_bus) {
pr_err("kvm: failed to shrink bus, removing it completely\n");
for (j = 0; j < bus->dev_count; j++) {
if (j == i)
@@ -4520,8 +4526,6 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
}
}
- rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
- synchronize_srcu_expedited(&kvm->srcu);
kfree(bus);
return;
}
--
2.31.1.295.g9ea45b61b8-goog
