From: Oliver Upton oupton@google.com
[ Upstream commit a44a4cc1c969afec97dbb2aedaf6f38eaa6253bb ]
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: Sasha Levin sashal@kernel.org --- virt/kvm/kvm_main.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 99c591569815..9134ae252d7c 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -911,7 +911,7 @@ static void kvm_destroy_vm_debugfs(struct kvm *kvm) int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc + kvm_vcpu_stats_header.num_desc;
- if (!kvm->debugfs_dentry) + if (IS_ERR(kvm->debugfs_dentry)) return;
debugfs_remove_recursive(kvm->debugfs_dentry); @@ -934,6 +934,12 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd) int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc + kvm_vcpu_stats_header.num_desc;
+ /* + * 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;
@@ -5373,7 +5379,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) } 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) {