Merge tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull fd prepare updates from Christian Brauner:
 "This adds the FD_ADD() and FD_PREPARE() primitive. They simplify the
  common pattern of get_unused_fd_flags() + create file + fd_install()
  that is used extensively throughout the kernel and currently requires
  cumbersome cleanup paths.

  FD_ADD() - For simple cases where a file is installed immediately:

      fd = FD_ADD(O_CLOEXEC, vfio_device_open_file(device));
      if (fd < 0)
          vfio_device_put_registration(device);
      return fd;

  FD_PREPARE() - For cases requiring access to the fd or file, or
  additional work before publishing:

      FD_PREPARE(fdf, O_CLOEXEC, sync_file->file);
      if (fdf.err) {
          fput(sync_file->file);
          return fdf.err;
      }

      data.fence = fd_prepare_fd(fdf);
      if (copy_to_user((void __user *)arg, &data, sizeof(data)))
          return -EFAULT;

      return fd_publish(fdf);

  The primitives are centered around struct fd_prepare. FD_PREPARE()
  encapsulates all allocation and cleanup logic and must be followed by
  a call to fd_publish() which associates the fd with the file and
  installs it into the caller's fdtable. If fd_publish() isn't called,
  both are deallocated automatically. FD_ADD() is a shorthand that does
  fd_publish() immediately and never exposes the struct to the caller.

  I've implemented this in a way that it's compatible with the cleanup
  infrastructure while also being usable separately. IOW, it's centered
  around struct fd_prepare which is aliased to class_fd_prepare_t and so
  we can make use of all the basica guard infrastructure"

* tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (42 commits)
  io_uring: convert io_create_mock_file() to FD_PREPARE()
  file: convert replace_fd() to FD_PREPARE()
  vfio: convert vfio_group_ioctl_get_device_fd() to FD_ADD()
  tty: convert ptm_open_peer() to FD_ADD()
  ntsync: convert ntsync_obj_get_fd() to FD_PREPARE()
  media: convert media_request_alloc() to FD_PREPARE()
  hv: convert mshv_ioctl_create_partition() to FD_ADD()
  gpio: convert linehandle_create() to FD_PREPARE()
  pseries: port papr_rtas_setup_file_interface() to FD_ADD()
  pseries: convert papr_platform_dump_create_handle() to FD_ADD()
  spufs: convert spufs_gang_open() to FD_PREPARE()
  papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE()
  spufs: convert spufs_context_open() to FD_PREPARE()
  net/socket: convert __sys_accept4_file() to FD_ADD()
  net/socket: convert sock_map_fd() to FD_ADD()
  net/kcm: convert kcm_ioctl() to FD_PREPARE()
  net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()
  secretmem: convert memfd_secret() to FD_ADD()
  memfd: convert memfd_create() to FD_ADD()
  bpf: convert bpf_token_create() to FD_PREPARE()
  ...

2 files changed, 6 insertions, 43 deletions

diff --git a/mm/memfd.c b/mm/memfd.c
index a405eaa451ee..805e297916e5 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -497,9 +497,9 @@ SYSCALL_DEFINE2(memfd_create,
 		const char __user *, uname,
 		unsigned int, flags)
 {
-	struct file *file;
-	int fd, error;
-	char *name;
+	char *name __free(kfree) = NULL;
+	unsigned int fd_flags;
+	int error;
 
 	error = sanitize_flags(&flags);
 	if (error < 0)
@@ -509,25 +509,6 @@ SYSCALL_DEFINE2(memfd_create,
 	if (IS_ERR(name))
 		return PTR_ERR(name);
 
-	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
-	if (fd < 0) {
-		error = fd;
-		goto err_free_name;
-	}
-
-	file = alloc_file(name, flags);
-	if (IS_ERR(file)) {
-		error = PTR_ERR(file);
-		goto err_free_fd;
-	}
-
-	fd_install(fd, file);
-	kfree(name);
-	return fd;
-
-err_free_fd:
-	put_unused_fd(fd);
-err_free_name:
-	kfree(name);
-	return error;
+	fd_flags = (flags & MFD_CLOEXEC) ? O_CLOEXEC : 0;
+	return FD_ADD(fd_flags, alloc_file(name, flags));
 }
diff --git a/mm/secretmem.c b/mm/secretmem.c
index b59350daffe3..f0ef4e198884 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -224,9 +224,6 @@ err_free_inode:
 
 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
 {
-	struct file *file;
-	int fd, err;
-
 	/* make sure local flags do not confict with global fcntl.h */
 	BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
 
@@ -238,22 +235,7 @@ SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
 	if (atomic_read(&secretmem_users) < 0)
 		return -ENFILE;
 
-	fd = get_unused_fd_flags(flags & O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	file = secretmem_file_create(flags);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto err_put_fd;
-	}
-
-	fd_install(fd, file);
-	return fd;
-
-err_put_fd:
-	put_unused_fd(fd);
-	return err;
+	return FD_ADD(flags & O_CLOEXEC, secretmem_file_create(flags));
 }
 
 static int secretmem_init_fs_context(struct fs_context *fc)