Merge tag 'vfs-7.2-rc1.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull openat2 updates from Christian Brauner:
 "Features:

   - Add O_EMPTYPATH to openat(2)/openat2(2). To get an operable file
     descriptor from an O_PATH file descriptor it is possible to use
     openat(fd, ".", O_DIRECTORY) for directories, but other file types
     require going through open("/proc/<pid>/fd/<nr>") and thus depend
     on a functioning procfs.

     With O_EMPTYPATH an empty path string is accepted and LOOKUP_EMPTY
     is set at path resolution time, allowing to reopen the file behind
     the file descriptor directly. Selftests are included.

   - Add an OPENAT2_REGULAR flag for openat2(2) which refuses to open
     anything but regular files with the new EFTYPE error code.

     This implements the "ability to only open regular files" feature
     requested by userspace via uapi-group.org and protects services
     from being redirected to fifos, device nodes, and friends.

     All atomic_open implementations were audited for OPENAT2_REGULAR
     handling. Explicit checks were added to ceph, gfs2, nfs (v4), and
     cifs/smb - these are the filesystems whose atomic_open can
     encounter an existing non-regular file and would otherwise call
     finish_open() on it or return a misleading error code.

     The remaining implementations (9p, fuse, vboxsf, nfs v2/v3) only
     call finish_open() on freshly created files and use
     finish_no_open() for lookup hits, letting the VFS catch non-regular
     files via the do_open() safety net.

  Cleanups:

   - Migrate the openat2 selftests to the kselftest harness and move
     them under selftests/filesystems/. The tests were written in the
     early days of selftests' TAP support and the modern kselftest
     harness is much easier to follow and maintain. The contents of the
     tests are unchanged and the new emptypath tests are ported on top.

   - Make the LAST_XXX last-type constants private to fs/namei.c. The
     only user outside of fs/namei.c was ksmbd which only needs to know
     whether the last component is a regular one, so
     vfs_path_parent_lookup() now performs the LAST_NORM check
     internally. The ints are replaced with a dedicated enum last_type"

* tag 'vfs-7.2-rc1.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  vfs: replace ints with enum last_type for LAST_XXX
  vfs: make LAST_XXX private to fs/namei.c
  selftests: openat2: port emptypath_test to kselftest harness
  kselftest/openat2: test for OPENAT2_REGULAR flag
  openat2: new OPENAT2_REGULAR flag support
  openat2: introduce EFTYPE error code
  selftest: add tests for O_EMPTYPATH
  vfs: add O_EMPTYPATH to openat(2)/openat2(2)
  selftests: openat2: migrate to kselftest harness
  selftests: openat2: switch from custom ARRAY_LEN to ARRAY_SIZE
  selftests: openat2: move helpers to header
  selftests: move openat2 tests to selftests/filesystems/

2 files changed, 45 insertions, 0 deletions

diff --git a/tools/include/uapi/asm-generic/errno.h b/tools/include/uapi/asm-generic/errno.h
index 92e7ae493ee3..bd78e69e0a43 100644
--- a/tools/include/uapi/asm-generic/errno.h
+++ b/tools/include/uapi/asm-generic/errno.h
@@ -122,4 +122,6 @@
 
 #define EHWPOISON	133	/* Memory page has hardware error */
 
+#define EFTYPE		134	/* Wrong file type for the intended operation */
+
 #endif
diff --git a/tools/include/uapi/linux/openat2.h b/tools/include/uapi/linux/openat2.h
new file mode 100644
index 000000000000..4759c471676c
--- /dev/null
+++ b/tools/include/uapi/linux/openat2.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_OPENAT2_H
+#define _LINUX_OPENAT2_H
+
+#include <linux/types.h>
+
+/*
+ * Arguments for how openat2(2) should open the target path. If only @flags and
+ * @mode are non-zero, then openat2(2) operates very similarly to openat(2).
+ *
+ * However, unlike openat(2), unknown or invalid bits in @flags result in
+ * -EINVAL rather than being silently ignored. @mode must be zero unless one of
+ * {O_CREAT, O_TMPFILE} are set.
+ *
+ * @flags: O_* flags.
+ * @mode: O_CREAT/O_TMPFILE file mode.
+ * @resolve: RESOLVE_* flags.
+ */
+struct open_how {
+	__u64 flags;
+	__u64 mode;
+	__u64 resolve;
+};
+
+/* how->resolve flags for openat2(2). */
+#define RESOLVE_NO_XDEV		0x01 /* Block mount-point crossings
+					(includes bind-mounts). */
+#define RESOLVE_NO_MAGICLINKS	0x02 /* Block traversal through procfs-style
+					"magic-links". */
+#define RESOLVE_NO_SYMLINKS	0x04 /* Block traversal through all symlinks
+					(implies OEXT_NO_MAGICLINKS) */
+#define RESOLVE_BENEATH		0x08 /* Block "lexical" trickery like
+					"..", symlinks, and absolute
+					paths which escape the dirfd. */
+#define RESOLVE_IN_ROOT		0x10 /* Make all jumps to "/" and ".."
+					be scoped inside the dirfd
+					(similar to chroot(2)). */
+#define RESOLVE_CACHED		0x20 /* Only complete if resolution can be
+					completed through cached lookup. May
+					return -EAGAIN if that's not
+					possible. */
+
+#endif /* _LINUX_OPENAT2_H */