fuse: fuse_dev_ioctl_clone() should wait for device file to be initialized

Use fuse_get_dev() not __fuse_get_dev() on the old fd, since in the case of
synchronous INIT the caller will want to wait for the device file to be
available for cloning, just like I/O wants to wait instead of returning an
error.

Fixes: dfb84c3 ("fuse: allow synchronous FUSE_INIT")
Cc: stable@vger.kernel.org # v6.18
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Author: Miklos Szeredi

fs/fuse/dev.c

@@ -2597,9 +2597,8 @@ static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
 
 static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp)
 {
-	int res;
 	int oldfd;
-	struct fuse_dev *fud = NULL;
+	struct fuse_dev *fud;
 
 	if (get_user(oldfd, argp))
 		return -EFAULT;
@@ -2612,17 +2611,15 @@ static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp)
 	 * Check against file->f_op because CUSE
 	 * uses the same ioctl handler.
 	 */
-	if (fd_file(f)->f_op == file->f_op)
-		fud = __fuse_get_dev(fd_file(f));
+	if (fd_file(f)->f_op != file->f_op)
+		return -EINVAL;
 
-	res = -EINVAL;
-	if (fud) {
-		mutex_lock(&fuse_mutex);
-		res = fuse_device_clone(fud->fc, file);
-		mutex_unlock(&fuse_mutex);
-	}
+	fud = fuse_get_dev(fd_file(f));
+	if (IS_ERR(fud))
+		return PTR_ERR(fud);
 
-	return res;
+	guard(mutex)(&fuse_mutex);
+	return fuse_device_clone(fud->fc, file);
 }
 
 static long fuse_dev_ioctl_backing_open(struct file *file,