From: Sean Christopherson seanjc@google.com

mainline inclusion from mainline-v5.13-rc1 commit 2ee3757424be7c1cd1d0bbfa6db29a7edd82a250 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94VO4 CVE: CVE-2021-47061

--------------------------------

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@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20210412222050.876100-2-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Conflicts: virt/kvm/kvm_main.c Signed-off-by: Liu Shixin liushixin2@huawei.com --- 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 5f4f222c991f..b65bff740c24 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3878,7 +3878,13 @@ 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, (new_bus->dev_count - i) * sizeof(struct kvm_io_range)); - } 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) @@ -3887,8 +3893,6 @@ 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; }