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, 27 insertions, 4 deletions

diff --git a/include/uapi/linux/close_range.h b/include/uapi/linux/close_range.h
index 2d804281554c..7da9ed95258a 100644
--- a/include/uapi/linux/close_range.h
+++ b/include/uapi/linux/close_range.h
@@ -2,11 +2,34 @@
 #ifndef _UAPI_LINUX_CLOSE_RANGE_H
 #define _UAPI_LINUX_CLOSE_RANGE_H
 
-/* Unshare the file descriptor table before closing file descriptors. */
-#define CLOSE_RANGE_UNSHARE	(1U << 1)
+/*
+ * A macro of one of these names defined before this header is parsed, by
+ * a libc or by a program's own fallback, would replace the enumerator.
+ */
+#undef CLOSE_RANGE_UNSHARE
+#undef CLOSE_RANGE_CLOEXEC
+#undef CLOSE_RANGE_EXCEPT
+#undef CLOSE_RANGE_CLOEXEC_ONLY
 
-/* Set the FD_CLOEXEC bit instead of closing the file descriptor. */
-#define CLOSE_RANGE_CLOEXEC	(1U << 2)
+enum close_range_flags {
+	/* Unshare the file descriptor table before closing file descriptors. */
+	CLOSE_RANGE_UNSHARE	= (1U << 1),
+
+	/* Set the FD_CLOEXEC bit instead of closing the file descriptor. */
+	CLOSE_RANGE_CLOEXEC	= (1U << 2),
+
+	/* Act on every file descriptor outside of the given range instead. */
+	CLOSE_RANGE_EXCEPT	= (1U << 3),
+
+	/* Only close file descriptors that have the FD_CLOEXEC bit set. */
+	CLOSE_RANGE_CLOEXEC_ONLY	= (1U << 4),
+};
+
+/* Keep #ifdef working and let glibc skip its own definitions. */
+#define CLOSE_RANGE_UNSHARE		CLOSE_RANGE_UNSHARE
+#define CLOSE_RANGE_CLOEXEC		CLOSE_RANGE_CLOEXEC
+#define CLOSE_RANGE_EXCEPT		CLOSE_RANGE_EXCEPT
+#define CLOSE_RANGE_CLOEXEC_ONLY	CLOSE_RANGE_CLOEXEC_ONLY
 
 #endif /* _UAPI_LINUX_CLOSE_RANGE_H */