[PATCH 1/1] powerpc/kvm/book3s: Fixes possible 'use after release' of kvm

[Leonardo Bras]

Fixes a possible 'use after free' of kvm variable.
It does use mutex_unlock(&kvm->lock) after possible freeing a variable
with kvm_put_kvm(kvm).

Signed-off-by: Leonardo Bras <leona...@linux.ibm.com>
---
 arch/powerpc/kvm/book3s_64_vio.c | 3 +--
 virt/kvm/kvm_main.c              | 8 ++++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 5834db0a54c6..a402ead833b6 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -316,14 +316,13 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
 
        if (ret >= 0)
                list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables);
-       else
-               kvm_put_kvm(kvm);
 
        mutex_unlock(&kvm->lock);
 
        if (ret >= 0)
                return ret;
 
+       kvm_put_kvm(kvm);
        kfree(stt);
  fail_acct:
        account_locked_vm(current->mm, kvmppc_stt_pages(npages), false);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 13efc291b1c7..f37089b60d09 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2744,10 +2744,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 
id)
        /* Now it's all set up, let userspace reach it */
        kvm_get_kvm(kvm);
        r = create_vcpu_fd(vcpu);
-       if (r < 0) {
-               kvm_put_kvm(kvm);
+       if (r < 0)
                goto unlock_vcpu_destroy;
-       }
 
        kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
 
@@ -2771,6 +2769,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 
id)
        mutex_lock(&kvm->lock);
        kvm->created_vcpus--;
        mutex_unlock(&kvm->lock);
+       if (r < 0)
+               kvm_put_kvm(kvm);
        return r;
 }
 
@@ -3183,10 +3183,10 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
        kvm_get_kvm(kvm);
        ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | 
O_CLOEXEC);
        if (ret < 0) {
-               kvm_put_kvm(kvm);
                mutex_lock(&kvm->lock);
                list_del(&dev->vm_node);
                mutex_unlock(&kvm->lock);
+               kvm_put_kvm(kvm);
                ops->destroy(dev);
                return ret;
        }
-- 
2.23.0