Merge tag 'vfs-7.4-rc1.close_range' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull close_range updates from Christian Brauner:
 "This adds two new close_range() flags.

  CLOSE_RANGE_EXCEPT makes close_range() operate on all file descriptors
  outside of [fd, max_fd] instead of the ones inside. Alone it closes
  everything but the range. With CLOSE_RANGE_CLOEXEC it marks everything
  but the range close-on-exec. With CLOSE_RANGE_UNSHARE dup_fd() never
  takes a reference on what is dropped. So a task between
  clone(CLONE_FILES | CLONE_VM | CLONE_VFORK) and execve() that has the
  descriptors for the child in one window can shed the rest of the
  shared table in one call and nothing outside of the window is
  referenced by the child at any point.

  CLOSE_RANGE_CLOEXEC_ONLY closes the close-on-exec descriptors in the
  range and leaves everything else alone. Whatever the caller
  deliberately passes down, stdio, LISTEN_FDS, an inherited pipe, stays
  where it is. Combined with CLOSE_RANGE_EXCEPT it names the handful of
  close-on-exec descriptors that have to survive, the executable or an
  error pipe, and closes every other close-on-exec descriptor.

  Along the way dup_fd() stops copying a range in the middle of the
  table only to close it again. close_range(CLOSE_RANGE_UNSHARE) only
  avoided the copy when the range sat at the end of the table.

  Descriptors in a skipped range are never copied and no reference is
  taken on them, so ->flush() isn't called anymore for files from a
  table they were never part of. The flags are turned into an enum and
  selftests cover the window positions, the shared and the private table
  and the unshare form"

* tag 'vfs-7.4-rc1.close_range' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  selftests/core: test CLOSE_RANGE_CLOEXEC_ONLY
  file: add CLOSE_RANGE_CLOEXEC_ONLY
  file: let dup_fd() drop only close-on-exec descriptors
  selftests/core: test CLOSE_RANGE_EXCEPT
  file: add CLOSE_RANGE_EXCEPT
  close_range: turn the flags into an enum
  file: let dup_fd() drop everything outside of the range
  file: rename dup_fd()'s punch_hole to range
  selftests/core: test the hole CLOSE_RANGE_UNSHARE leaves behind
  file: let dup_fd() leave the punched hole behind

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index c45306a9f007..afdfaad381df 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -101,8 +101,17 @@ struct task_struct;
 
 void put_files_struct(struct files_struct *fs);
 int unshare_files(void);
+enum fd_range_flags {
+	/* Leave behind all descriptors outside of the specified range. */
+	FD_RANGE_EXCEPT		= (1U << 0),
+
+	/* Only select descriptors that have close-on-exec set. */
+	FD_RANGE_CLOEXEC_ONLY	= (1U << 1),
+};
+
 struct fd_range {
 	unsigned int from, to;
+	enum fd_range_flags flags;
 };
 struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __latent_entropy;
 void do_close_on_exec(struct files_struct *);