diff mbox series

[v3,4/6] KVM: Pass the name of the VM fd to kvm_create_vm_debugfs()

Message ID 20220720092259.3491733-5-oliver.upton@linux.dev (mailing list archive)
State New, archived
Headers show
Series KVM: Clean up debugfs init/destroy | expand

Commit Message

Oliver Upton July 20, 2022, 9:22 a.m. UTC 
From: Oliver Upton <oupton@google.com>

At the time the VM fd is used in kvm_create_vm_debugfs(), the fd has
been allocated but not yet installed. It is only really useful as an
identifier in strings for the VM (such as debugfs).

Treat it exactly as such by passing the string name of the fd to
kvm_create_vm_debugfs(), futureproofing against possible misuse of the
VM fd.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 virt/kvm/kvm_main.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Sean Christopherson Aug. 5, 2022, 7:20 p.m. UTC | #1 
On Wed, Jul 20, 2022, Oliver Upton wrote:
> From: Oliver Upton <oupton@google.com>
> 
> At the time the VM fd is used in kvm_create_vm_debugfs(), the fd has
> been allocated but not yet installed. It is only really useful as an
> identifier in strings for the VM (such as debugfs).
> 
> Treat it exactly as such by passing the string name of the fd to
> kvm_create_vm_debugfs(), futureproofing against possible misuse of the
> VM fd.

One last whine session,

  kvm_create_vm_debugfs() to guard against attempts to consume the fd
  before it is installed.

> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Oliver Upton <oupton@google.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>
diff mbox series

Patch

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e270cff3c9f4..1e7f780a357b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1021,7 +1021,7 @@  static void kvm_destroy_vm_debugfs(struct kvm *kvm)
 	}
 }
 
-static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
+static int kvm_create_vm_debugfs(struct kvm *kvm, const char *fdname)
 {
 	static DEFINE_MUTEX(kvm_debugfs_lock);
 	struct dentry *dent;
@@ -1035,7 +1035,7 @@  static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
 	if (!debugfs_initialized())
 		return 0;
 
-	snprintf(dir_name, sizeof(dir_name), "%d-%d", task_pid_nr(current), fd);
+	snprintf(dir_name, sizeof(dir_name), "%d-%s", task_pid_nr(current), fdname);
 	mutex_lock(&kvm_debugfs_lock);
 	dent = debugfs_lookup(dir_name, kvm_debugfs_dir);
 	if (dent) {
@@ -4889,6 +4889,7 @@  EXPORT_SYMBOL_GPL(file_is_kvm);
 
 static int kvm_dev_ioctl_create_vm(unsigned long type)
 {
+	char fdname[ITOA_MAX_LEN + 1];
 	int r, fd;
 	struct kvm *kvm;
 	struct file *file;
@@ -4897,6 +4898,8 @@  static int kvm_dev_ioctl_create_vm(unsigned long type)
 	if (fd < 0)
 		return fd;
 
+	snprintf(fdname, sizeof(fdname), "%d", fd);
+
 	kvm = kvm_create_vm(type);
 	if (IS_ERR(kvm)) {
 		r = PTR_ERR(kvm);
@@ -4920,7 +4923,7 @@  static int kvm_dev_ioctl_create_vm(unsigned long type)
 	 * cases it will be called by the final fput(file) and will take
 	 * care of doing kvm_put_kvm(kvm).
 	 */
-	if (kvm_create_vm_debugfs(kvm, fd) < 0) {
+	if (kvm_create_vm_debugfs(kvm, fdname) < 0) {
 		fput(file);
 		r = -ENOMEM;
 		goto put_fd;