From: Oliver Upton <oupton@xxxxxxxxxx> commit a44a4cc1c969afec97dbb2aedaf6f38eaa6253bb upstream. Unfortunately, there is no guarantee that KVM was able to instantiate a debugfs directory for a particular VM. To that end, KVM shouldn't even attempt to create new debugfs files in this case. If the specified parent dentry is NULL, debugfs_create_file() will instantiate files at the root of debugfs. For arm64, it is possible to create the vgic-state file outside of a VM directory, the file is not cleaned up when a VM is destroyed. Nonetheless, the corresponding struct kvm is freed when the VM is destroyed. Nip the problem in the bud for all possible errant debugfs file creations by initializing kvm->debugfs_dentry to -ENOENT. In so doing, debugfs_create_file() will fail instead of creating the file in the root directory. Cc: stable@xxxxxxxxxx Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions") Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220406235615.1447180-2-oupton@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- virt/kvm/kvm_main.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -610,7 +610,7 @@ static void kvm_destroy_vm_debugfs(struc { int i; - if (!kvm->debugfs_dentry) + if (IS_ERR(kvm->debugfs_dentry)) return; debugfs_remove_recursive(kvm->debugfs_dentry); @@ -628,6 +628,12 @@ static int kvm_create_vm_debugfs(struct struct kvm_stat_data *stat_data; struct kvm_stats_debugfs_item *p; + /* + * Force subsequent debugfs file creations to fail if the VM directory + * is not created. + */ + kvm->debugfs_dentry = ERR_PTR(-ENOENT); + if (!debugfs_initialized()) return 0; Patches currently in stable-queue which might be from oupton@xxxxxxxxxx are queue-4.19/kvm-don-t-create-vm-debugfs-files-outside-of-the-vm-directory.patch