From: Oliver Upton oupton@google.com
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@kernel.org Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions") Signed-off-by: Oliver Upton oupton@google.com Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20220406235615.1447180-2-oupton@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- virt/kvm/kvm_main.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -673,7 +673,7 @@ 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); @@ -693,6 +693,12 @@ 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;
@@ -4731,7 +4737,7 @@ static void kvm_uevent_notify_change(uns } add_uevent_var(env, "PID=%d", kvm->userspace_pid);
- if (kvm->debugfs_dentry) { + if (!IS_ERR(kvm->debugfs_dentry)) { char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);
if (p) {