diff options
| author | Oliver Upton <oliver.upton@linux.dev> | 2024-04-22 20:01:40 +0000 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2024-04-25 13:19:55 +0100 |
| commit | ea54dd374232cc3b6d0ac0a89d715d61ebb04bf6 (patch) | |
| tree | da27fc03564121f8a37927d596f93b4ab0832ea9 /virt | |
| parent | fec50db7033ea478773b159e0e2efb135270e3b7 (diff) | |
KVM: Treat the device list as an rculist
A subsequent change to KVM/arm64 will necessitate walking the device
list outside of the kvm->lock. Prepare by converting to an rculist. This
has zero effect on the VM destruction path, as it is expected every
reader is backed by a reference on the kvm struct.
On the other hand, ensure a given device is completely destroyed before
dropping the kvm->lock in the release() path, as certain devices expect
to be a singleton (e.g. the vfio-kvm device).
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20240422200158.2606761-2-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/kvm_main.c | 14 | ||||
| -rw-r--r-- | virt/kvm/vfio.c | 2 |
2 files changed, 13 insertions, 3 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fb49c2a60200..6c09fe40948f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1329,6 +1329,12 @@ static void kvm_destroy_devices(struct kvm *kvm) * We do not need to take the kvm->lock here, because nobody else * has a reference to the struct kvm at this point and therefore * cannot access the devices list anyhow. + * + * The device list is generally managed as an rculist, but list_del() + * is used intentionally here. If a bug in KVM introduced a reader that + * was not backed by a reference on the kvm struct, the hope is that + * it'd consume the poisoned forward pointer instead of suffering a + * use-after-free, even though this cannot be guaranteed. */ list_for_each_entry_safe(dev, tmp, &kvm->devices, vm_node) { list_del(&dev->vm_node); @@ -4725,7 +4731,8 @@ static int kvm_device_release(struct inode *inode, struct file *filp) if (dev->ops->release) { mutex_lock(&kvm->lock); - list_del(&dev->vm_node); + list_del_rcu(&dev->vm_node); + synchronize_rcu(); dev->ops->release(dev); mutex_unlock(&kvm->lock); } @@ -4808,7 +4815,7 @@ static int kvm_ioctl_create_device(struct kvm *kvm, kfree(dev); return ret; } - list_add(&dev->vm_node, &kvm->devices); + list_add_rcu(&dev->vm_node, &kvm->devices); mutex_unlock(&kvm->lock); if (ops->init) @@ -4819,7 +4826,8 @@ static int kvm_ioctl_create_device(struct kvm *kvm, if (ret < 0) { kvm_put_kvm_no_destroy(kvm); mutex_lock(&kvm->lock); - list_del(&dev->vm_node); + list_del_rcu(&dev->vm_node); + synchronize_rcu(); if (ops->release) ops->release(dev); mutex_unlock(&kvm->lock); diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c index ca24ce120906..76b7f6085dcd 100644 --- a/virt/kvm/vfio.c +++ b/virt/kvm/vfio.c @@ -366,6 +366,8 @@ static int kvm_vfio_create(struct kvm_device *dev, u32 type) struct kvm_device *tmp; struct kvm_vfio *kv; + lockdep_assert_held(&dev->kvm->lock); + /* Only one VFIO "device" per VM */ list_for_each_entry(tmp, &dev->kvm->devices, vm_node) if (tmp->ops == &kvm_vfio_ops) |