KVM: Get an fd before creating the VM

Allocate a VM's fd at the very beginning of kvm_dev_ioctl_create_vm() so
that KVM can use the fd value to generate strigns, e.g. for debugfs,
when creating and initializing the VM.

Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20220720092259.3491733-4-oliver.upton@linux.dev>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f601428e0cc87bce5aa79e3746f6d593f3468524..eeb084a9cb7012d73d92b51beae47e47be2dddf0 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4889,25 +4889,27 @@ EXPORT_SYMBOL_GPL(file_is_kvm);
 
 static int kvm_dev_ioctl_create_vm(unsigned long type)
 {
-       int r;
+       int r, fd;
        struct kvm *kvm;
        struct file *file;
 
+       fd = get_unused_fd_flags(O_CLOEXEC);
+       if (fd < 0)
+               return fd;
+
        kvm = kvm_create_vm(type);
-       if (IS_ERR(kvm))
-               return PTR_ERR(kvm);
+       if (IS_ERR(kvm)) {
+               r = PTR_ERR(kvm);
+               goto put_fd;
+       }
+
 #ifdef CONFIG_KVM_MMIO
        r = kvm_coalesced_mmio_init(kvm);
        if (r < 0)
                goto put_kvm;
 #endif
-       r = get_unused_fd_flags(O_CLOEXEC);
-       if (r < 0)
-               goto put_kvm;
-
        file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
        if (IS_ERR(file)) {
-               put_unused_fd(r);
                r = PTR_ERR(file);
                goto put_kvm;
        }
@@ -4918,18 +4920,20 @@ 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, r) < 0) {
-               put_unused_fd(r);
+       if (kvm_create_vm_debugfs(kvm, fd) < 0) {
                fput(file);
-               return -ENOMEM;
+               r = -ENOMEM;
+               goto put_fd;
        }
        kvm_uevent_notify_change(KVM_EVENT_CREATE_VM, kvm);
 
-       fd_install(r, file);
-       return r;
+       fd_install(fd, file);
+       return fd;
 
 put_kvm:
        kvm_put_kvm(kvm);
+put_fd:
+       put_unused_fd(fd);
        return r;
 }