Hi Greg,
On Mon, Apr 18, 2022 at 5:24 AM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
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
Can you drop this patch from stable for the time being? There's a bug in it because KVM does init/destroy awkwardly. Sean working on a fix [1].
[1]: https://lore.kernel.org/kvm/20220415004622.2207751-1-seanjc@google.com/
-- Thanks, Oliver