lchown: detect Solaris and FreeBSD bug

Solaris 9 and FreeBSD 7.2 lchown("link-to-file/",uid,gid)
mistakenly changes ownership of "file".

* lib/lchown.c (rpl_lchown): Work around bug.
* m4/lchown.m4 (gl_FUNC_LCHOWN): Check for trailing slash bugs.
* m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Add witness.
* modules/unistd (Makefile.am): Populate it.
* lib/unistd.in.h (lchown): Update declaration.
* doc/posix-functions/lchown.texi (lchown): Document the bug.
* modules/lchown-tests: New file.
* tests/test-lchown.h (test_lchown): Likewise.
* tests/test-lchown.c (main): Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>

11 files changed, 448 insertions, 15 deletions

diff --git a/ChangeLog b/ChangeLog
index 8ca5ad6b64..f0e2a18df5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2009-11-14  Eric Blake  <ebb9@byu.net>
 
+	lchown: detect Solaris and FreeBSD bug
+	* lib/lchown.c (rpl_lchown): Work around bug.
+	* m4/lchown.m4 (gl_FUNC_LCHOWN): Check for trailing slash bugs.
+	* m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Add witness.
+	* modules/unistd (Makefile.am): Populate it.
+	* lib/unistd.in.h (lchown): Update declaration.
+	* doc/posix-functions/lchown.texi (lchown): Document the bug.
+	* modules/lchown-tests: New file.
+	* tests/test-lchown.h (test_lchown): Likewise.
+	* tests/test-lchown.c (main): Likewise.
+
 	chown: detect Solaris and FreeBSD bug
 	* lib/chown.c (rpl_chown): Work around bug.
 	* m4/chown.m4 (gl_FUNC_CHOWN): Check for trailing slash bugs.
diff --git a/doc/posix-functions/lchown.texi b/doc/posix-functions/lchown.texi
index e40be3fdab..0686bf3917 100644
--- a/doc/posix-functions/lchown.texi
+++ b/doc/posix-functions/lchown.texi
@@ -9,7 +9,13 @@ Gnulib module: lchown
 Portability problems fixed by Gnulib:
 @itemize
 @item
-This function is missing on some platforms:
+Some platforms fail to detect trailing slash on non-directories, as in
+@code{lchown("link-to-file/",uid,gid)}:
+FreeBSD 7.2, Solaris 9.
+@item
+This function is missing on some platforms; however, the replacement
+fails on symlinks if @code{chown} is supported, and fails altogether
+with @code{ENOSYS} otherwise:
 MacOS X 10.3, mingw, BeOS.
 @end itemize
 
diff --git a/lib/lchown.c b/lib/lchown.c
index 65434b45cc..265c2f72ec 100644
--- a/lib/lchown.c
+++ b/lib/lchown.c
@@ -23,13 +23,16 @@
 #include <unistd.h>
 
 #include <errno.h>
+#include <string.h>
 #include <sys/stat.h>
 
+#if !HAVE_LCHOWN
+
 /* If the system chown does not follow symlinks, we don't want it
    replaced by gnulib's chown, which does follow symlinks.  */
-#if CHOWN_MODIFIES_SYMLINK
-# undef chown
-#endif
+# if CHOWN_MODIFIES_SYMLINK
+#  undef chown
+# endif
 
 /* Work just like chown, except when FILE is a symbolic link.
    In that case, set errno to EOPNOTSUPP and return -1.
@@ -39,8 +42,8 @@
 int
 lchown (const char *file, uid_t uid, gid_t gid)
 {
-#if HAVE_CHOWN
-# if ! CHOWN_MODIFIES_SYMLINK
+# if HAVE_CHOWN
+#  if ! CHOWN_MODIFIES_SYMLINK
   struct stat stats;
 
   if (lstat (file, &stats) == 0 && S_ISLNK (stats.st_mode))
@@ -48,12 +51,28 @@ lchown (const char *file, uid_t uid, gid_t gid)
       errno = EOPNOTSUPP;
       return -1;
     }
-# endif
+#  endif
 
   return chown (file, uid, gid);
 
-#else /* !HAVE_CHOWN */
+# else /* !HAVE_CHOWN */
   errno = ENOSYS;
   return -1;
-#endif
+# endif
 }
+
+#else /* HAVE_LCHOWN */
+
+# undef lchown
+
+/* Work around trailing slash bugs in lchown.  */
+int
+rpl_lchown (const char *file, uid_t uid, gid_t gid)
+{
+  size_t len = strlen (file);
+  if (len && file[len - 1] == '/')
+    return chown (file, uid, gid);
+  return lchown (file, uid, gid);
+}
+
+#endif /* HAVE_LCHOWN */
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 6b0513bdda..c026b71784 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -565,12 +565,15 @@ extern void endusershell (void);
 
 #if @GNULIB_LCHOWN@
 # if @REPLACE_LCHOWN@
+#  undef lchown
+#  define lchown rpl_lchown
+# endif
+# if !@HAVE_LCHOWN@ || @REPLACE_LCHOWN@
 /* Change the owner of FILE to UID (if UID is not -1) and the group of FILE
    to GID (if GID is not -1).  Do not follow symbolic links.
    Return 0 if successful, otherwise -1 and errno set.
    See the POSIX:2001 specification
    <http://www.opengroup.org/susv3xsh/lchown.html>.  */
-#  define lchown rpl_lchown
 extern int lchown (char const *file, uid_t owner, gid_t group);
 # endif
 #elif defined GNULIB_POSIXCHECK
diff --git a/m4/lchown.m4 b/m4/lchown.m4
index f509fde04a..e40c437626 100644
--- a/m4/lchown.m4
+++ b/m4/lchown.m4
@@ -1,14 +1,16 @@
-# serial 13
+# serial 14
 # Determine whether we need the lchown wrapper.
 
-dnl Copyright (C) 1998, 2001, 2003-2007, 2009 Free Software Foundation, Inc.
+dnl Copyright (C) 1998, 2001, 2003-2007, 2009 Free Software
+dnl Foundation, Inc.
 
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Jim Meyering.
-dnl Provide lchown on systems that lack it.
+dnl Provide lchown on systems that lack it, and work around trailing
+dnl slash bugs on systems that have it.
 
 AC_DEFUN([gl_FUNC_LCHOWN],
 [
@@ -16,6 +18,10 @@ AC_DEFUN([gl_FUNC_LCHOWN],
   AC_REQUIRE([gl_FUNC_CHOWN])
   AC_REPLACE_FUNCS([lchown])
   if test $ac_cv_func_lchown = no; then
+    HAVE_LCHOWN=0
+  elif test "$gl_cv_func_chown_slash_works" != yes; then
+    dnl Trailing slash bugs in chown also occur in lchown.
+    AC_LIBOBJ([lchown])
     REPLACE_LCHOWN=1
   fi
 ])
diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4
index bd368c6144..88e60a0538 100644
--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -1,4 +1,4 @@
-# unistd_h.m4 serial 33
+# unistd_h.m4 serial 34
 dnl Copyright (C) 2006-2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -82,6 +82,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   HAVE_GETHOSTNAME=1;     AC_SUBST([HAVE_GETHOSTNAME])
   HAVE_GETPAGESIZE=1;     AC_SUBST([HAVE_GETPAGESIZE])
   HAVE_GETUSERSHELL=1;    AC_SUBST([HAVE_GETUSERSHELL])
+  HAVE_LCHOWN=1;          AC_SUBST([HAVE_LCHOWN])
   HAVE_LINK=1;            AC_SUBST([HAVE_LINK])
   HAVE_LINKAT=1;          AC_SUBST([HAVE_LINKAT])
   HAVE_PIPE2=1;           AC_SUBST([HAVE_PIPE2])
diff --git a/modules/lchown b/modules/lchown
index c50537aac2..233e334790 100644
--- a/modules/lchown
+++ b/modules/lchown
@@ -25,4 +25,4 @@ License:
 GPL
 
 Maintainer:
-Jim Meyering
+Jim Meyering, Eric Blake
diff --git a/modules/lchown-tests b/modules/lchown-tests
new file mode 100644
index 0000000000..c33103a6b3
--- /dev/null
+++ b/modules/lchown-tests
@@ -0,0 +1,19 @@
+Files:
+tests/test-lchown.h
+tests/test-lchown.c
+
+Depends-on:
+mgetgroups
+progname
+sleep
+stat-time
+stdbool
+symlink
+
+configure.ac:
+AC_CHECK_FUNCS_ONCE([getegid usleep])
+
+Makefile.am:
+TESTS += test-lchown
+check_PROGRAMS += test-lchown
+test_lchown_LDADD = $(LDADD) @LIBINTL@
diff --git a/modules/unistd b/modules/unistd
index 031d7076e0..1cb3b0b629 100644
--- a/modules/unistd
+++ b/modules/unistd
@@ -74,6 +74,7 @@ unistd.h: unistd.in.h
 	      -e 's|@''HAVE_GETHOSTNAME''@|$(HAVE_GETHOSTNAME)|g' \
 	      -e 's|@''HAVE_GETPAGESIZE''@|$(HAVE_GETPAGESIZE)|g' \
 	      -e 's|@''HAVE_GETUSERSHELL''@|$(HAVE_GETUSERSHELL)|g' \
+	      -e 's|@''HAVE_LCHOWN''@|$(HAVE_LCHOWN)|g' \
 	      -e 's|@''HAVE_LINK''@|$(HAVE_LINK)|g' \
 	      -e 's|@''HAVE_LINKAT''@|$(HAVE_LINKAT)|g' \
 	      -e 's|@''HAVE_PIPE2''@|$(HAVE_PIPE2)|g' \
diff --git a/tests/test-lchown.c b/tests/test-lchown.c
new file mode 100644
index 0000000000..78c2940819
--- /dev/null
+++ b/tests/test-lchown.c
@@ -0,0 +1,56 @@
+/* Tests of lchown.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2009.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+#include "mgetgroups.h"
+#include "stat-time.h"
+
+#define ASSERT(expr) \
+  do                                                                         \
+    {                                                                        \
+      if (!(expr))                                                           \
+        {                                                                    \
+          fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__);  \
+          fflush (stderr);                                                   \
+          abort ();                                                          \
+        }                                                                    \
+    }                                                                        \
+  while (0)
+
+#define BASE "test-lchown.t"
+
+#include "test-lchown.h"
+
+int
+main (void)
+{
+  /* Remove any leftovers from a previous partial run.  */
+  ASSERT (system ("rm -rf " BASE "*") == 0);
+
+  return test_lchown (lchown, true);
+}
diff --git a/tests/test-lchown.h b/tests/test-lchown.h
new file mode 100644
index 0000000000..b0987c51cc
--- /dev/null
+++ b/tests/test-lchown.h
@@ -0,0 +1,311 @@
+/* Tests of lchown.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2009.  */
+
+#ifndef TEST_CHOWN_NAP
+/* Sleep long enough to notice a timestamp difference on the file
+   system in the current directory.  */
+static void
+nap (void)
+{
+# if !HAVE_USLEEP
+  /* Assume the worst case file system of FAT, which has a granularity
+     of 2 seconds.  */
+  sleep (2);
+# else /* HAVE_USLEEP */
+  static long delay;
+  if (!delay)
+    {
+      /* Initialize only once, by sleeping for 20 milliseconds (needed
+         since xfs has a quantization of about 10 milliseconds, even
+         though it has a granularity of 1 nanosecond, and since NTFS
+         has a default quantization of 15.25 milliseconds, even though
+         it has a granularity of 100 nanoseconds).  If the seconds
+         differ, repeat the test one more time (in case we crossed a
+         quantization boundary on a file system with 1 second
+         resolution).  If we can't observe a difference in only the
+         nanoseconds, then fall back to 2 seconds.  However, note that
+         usleep (2000000) is allowed to fail with EINVAL.  */
+      struct stat st1;
+      struct stat st2;
+      ASSERT (close (creat (BASE "tmp", 0600)) == 0);
+      ASSERT (stat (BASE "tmp", &st1) == 0);
+      ASSERT (unlink (BASE "tmp") == 0);
+      delay = 20000;
+      usleep (delay);
+      ASSERT (close (creat (BASE "tmp", 0600)) == 0);
+      ASSERT (stat (BASE "tmp", &st2) == 0);
+      ASSERT (unlink (BASE "tmp") == 0);
+      if (st1.st_mtime != st2.st_mtime)
+        {
+          /* Seconds differ, give it one more shot.  */
+          st1 = st2;
+          usleep (delay);
+          ASSERT (close (creat (BASE "tmp", 0600)) == 0);
+          ASSERT (stat (BASE "tmp", &st2) == 0);
+          ASSERT (unlink (BASE "tmp") == 0);
+        }
+      if (! (st1.st_mtime == st2.st_mtime
+             && get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2)))
+        delay = 2000000;
+    }
+  if (delay == 2000000)
+    sleep (2);
+  else
+    usleep (delay);
+# endif /* HAVE_USLEEP */
+}
+#endif /* !TEST_CHOWN_NAP */
+
+#if !HAVE_GETEGID
+# define getegid() (-1)
+#endif
+
+/* This file is designed to test lchown(n,o,g) and
+   chownat(AT_FDCWD,n,o,g,AT_SYMLINK_NOFOLLOW).  FUNC is the function
+   to test.  Assumes that BASE and ASSERT are already defined, and
+   that appropriate headers are already included.  If PRINT, warn
+   before skipping symlink tests with status 77.  */
+
+static int
+test_lchown (int (*func) (char const *, uid_t, gid_t), bool print)
+{
+  struct stat st1;
+  struct stat st2;
+  gid_t *gids = NULL;
+  int gids_count;
+  int result;
+
+  /* Solaris 8 is interesting - if the current process belongs to
+     multiple groups, the current directory is owned by a a group that
+     the current process belongs to but different than getegid(), and
+     the current directory does not have the S_ISGID bit, then regular
+     files created in the directory belong to the directory's group,
+     but symlinks belong to the current effective group id.  If
+     S_ISGID is set, then both files and symlinks belong to the
+     directory's group.  However, it is possible to run the testsuite
+     from within a directory owned by a group we don't belong to, in
+     which case all things that we create belong to the current
+     effective gid.  So, work around the issues by creating a
+     subdirectory (we are guaranteed that the subdirectory will be
+     owned by one of our current groups), change ownership of that
+     directory to the current effective gid (which will thus succeed),
+     then create all other files within that directory (eliminating
+     questions on whether inheritance or current id triumphs, since
+     the two methods resolve to the same gid).  */
+  ASSERT (mkdir (BASE "dir", 0700) == 0);
+  ASSERT (stat (BASE "dir", &st1) == 0);
+
+  /* Filter out mingw, which has no concept of groups.  */
+  result = func (BASE "dir", st1.st_uid, getegid ());
+  if (result == -1 && errno == ENOSYS)
+    {
+      ASSERT (rmdir (BASE "dir") == 0);
+      if (print)
+        fputs ("skipping test: no support for ownership\n", stderr);
+      return 77;
+    }
+  ASSERT (result == 0);
+
+  ASSERT (close (creat (BASE "dir/file", 0600)) == 0);
+  ASSERT (stat (BASE "dir/file", &st1) == 0);
+  ASSERT (st1.st_uid != -1);
+  ASSERT (st1.st_gid != -1);
+  ASSERT (st1.st_gid == getegid ());
+
+  /* Sanity check of error cases.  */
+  errno = 0;
+  ASSERT (func ("", -1, -1) == -1);
+  ASSERT (errno == ENOENT);
+  errno = 0;
+  ASSERT (func ("no_such", -1, -1) == -1);
+  ASSERT (errno == ENOENT);
+  errno = 0;
+  ASSERT (func ("no_such/", -1, -1) == -1);
+  ASSERT (errno == ENOENT);
+  errno = 0;
+  ASSERT (func (BASE "dir/file/", -1, -1) == -1);
+  ASSERT (errno == ENOTDIR);
+
+  /* Check that -1 does not alter ownership.  */
+  ASSERT (func (BASE "dir/file", -1, st1.st_gid) == 0);
+  ASSERT (func (BASE "dir/file", st1.st_uid, -1) == 0);
+  ASSERT (stat (BASE "dir/file", &st2) == 0);
+  ASSERT (st1.st_uid == st2.st_uid);
+  ASSERT (st1.st_gid == st2.st_gid);
+
+  /* Even if the values aren't changing, ctime is required to change
+     if at least one argument is not -1.  */
+  nap ();
+  ASSERT (func (BASE "dir/file", st1.st_uid, st1.st_gid) == 0);
+  ASSERT (stat (BASE "dir/file", &st2) == 0);
+  ASSERT (st1.st_ctime < st2.st_ctime
+          || (st1.st_ctime == st2.st_ctime
+              && get_stat_ctime_ns (&st1) < get_stat_ctime_ns (&st2)));
+
+  /* Test symlink behavior.  */
+  if (symlink ("link", BASE "dir/link2"))
+    {
+      ASSERT (unlink (BASE "dir/file") == 0);
+      ASSERT (rmdir (BASE "dir") == 0);
+      if (print)
+        fputs ("skipping test: symlinks not supported on this file system\n",
+               stderr);
+      return 77;
+    }
+  result = func (BASE "dir/link2", -1, -1);
+  if (result == -1 && errno == ENOSYS)
+    {
+      ASSERT (unlink (BASE "dir/file") == 0);
+      ASSERT (unlink (BASE "dir/link2") == 0);
+      ASSERT (rmdir (BASE "dir") == 0);
+      if (print)
+        fputs ("skipping test: symlink ownership not supported\n", stderr);
+      return 77;
+    }
+  ASSERT (result == 0);
+  errno = 0;
+  ASSERT (func (BASE "dir/link2/", st1.st_uid, st1.st_gid) == -1);
+  ASSERT (errno == ENOENT);
+  ASSERT (symlink ("file", BASE "dir/link") == 0);
+  ASSERT (mkdir (BASE "dir/sub", 0700) == 0);
+  ASSERT (symlink ("sub", BASE "dir/link3") == 0);
+
+  /* For non-privileged users, lchown can only portably succeed at
+     changing group ownership of a file we own.  If we belong to at
+     least two groups, then verifying the correct change is simple.
+     But if we belong to only one group, then we fall back on the
+     other observable effect of lchown: the ctime must be updated.
+     Be careful of duplicates returned by getgroups.  */
+  gids_count = mgetgroups (NULL, -1, &gids);
+  if (2 <= gids_count && gids[0] == gids[1] && 2 < gids_count--)
+    gids[1] = gids[2];
+  if (1 < gids_count || (gids_count == 1 && gids[0] != st1.st_gid))
+    {
+      if (gids[0] == st1.st_gid)
+        {
+          ASSERT (1 < gids_count);
+          ASSERT (gids[0] != gids[1]);
+          gids[0] = gids[1];
+        }
+      ASSERT (gids[0] != st1.st_gid);
+      ASSERT (gids[0] != -1);
+      ASSERT (lstat (BASE "dir/link", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/link2", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+
+      errno = 0;
+      ASSERT (func (BASE "dir/link2/", -1, gids[0]) == -1);
+      ASSERT (errno == ENOTDIR);
+      ASSERT (stat (BASE "dir/file", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/link", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/link2", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+
+      ASSERT (func (BASE "dir/link2", -1, gids[0]) == 0);
+      ASSERT (stat (BASE "dir/file", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/link", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/link2", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (gids[0] == st2.st_gid);
+
+      /* Trailing slash follows through to directory.  */
+      ASSERT (lstat (BASE "dir/link3", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/sub", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+
+      ASSERT (func (BASE "dir/link3/", -1, gids[0]) == 0);
+      ASSERT (lstat (BASE "dir/link3", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (st1.st_gid == st2.st_gid);
+      ASSERT (lstat (BASE "dir/sub", &st2) == 0);
+      ASSERT (st1.st_uid == st2.st_uid);
+      ASSERT (gids[0] == st2.st_gid);
+    }
+  else
+    {
+      struct stat l1;
+      struct stat l2;
+      ASSERT (stat (BASE "dir/file", &st1) == 0);
+      ASSERT (lstat (BASE "dir/link", &l1) == 0);
+      ASSERT (lstat (BASE "dir/link2", &l2) == 0);
+
+      nap ();
+      errno = 0;
+      ASSERT (func (BASE "dir/link2/", -1, st1.st_gid) == -1);
+      ASSERT (errno == ENOTDIR);
+      ASSERT (stat (BASE "dir/file", &st2) == 0);
+      ASSERT (st1.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&st1) == get_stat_ctime_ns (&st2));
+      ASSERT (lstat (BASE "dir/link", &st2) == 0);
+      ASSERT (l1.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&l1) == get_stat_ctime_ns (&st2));
+      ASSERT (lstat (BASE "dir/link2", &st2) == 0);
+      ASSERT (l2.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&l2) == get_stat_ctime_ns (&st2));
+
+      ASSERT (func (BASE "dir/link2", -1, gids[0]) == 0);
+      ASSERT (stat (BASE "dir/file", &st2) == 0);
+      ASSERT (st1.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&st1) == get_stat_ctime_ns (&st2));
+      ASSERT (lstat (BASE "dir/link", &st2) == 0);
+      ASSERT (l1.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&l1) == get_stat_ctime_ns (&st2));
+      ASSERT (lstat (BASE "dir/link2", &st2) == 0);
+      ASSERT (l2.st_ctime < st2.st_ctime
+              || (l2.st_ctime == st2.st_ctime
+                  && get_stat_ctime_ns (&l2) < get_stat_ctime_ns (&st2)));
+
+      /* Trailing slash follows through to directory.  */
+      ASSERT (lstat (BASE "dir/sub", &st1) == 0);
+      ASSERT (lstat (BASE "dir/link3", &l1) == 0);
+      nap ();
+      ASSERT (func (BASE "dir/link3/", -1, gids[0]) == 0);
+      ASSERT (lstat (BASE "dir/link3", &st2) == 0);
+      ASSERT (l1.st_ctime == st2.st_ctime);
+      ASSERT (get_stat_ctime_ns (&l1) == get_stat_ctime_ns (&st2));
+      ASSERT (lstat (BASE "dir/sub", &st2) == 0);
+      ASSERT (st1.st_ctime < st2.st_ctime
+              || (st1.st_ctime == st2.st_ctime
+                  && get_stat_ctime_ns (&st1) < get_stat_ctime_ns (&st2)));
+    }
+
+  /* Cleanup.  */
+  free (gids);
+  ASSERT (unlink (BASE "dir/file") == 0);
+  ASSERT (unlink (BASE "dir/link") == 0);
+  ASSERT (unlink (BASE "dir/link2") == 0);
+  ASSERT (unlink (BASE "dir/link3") == 0);
+  ASSERT (rmdir (BASE "dir/sub") == 0);
+  ASSERT (rmdir (BASE "dir") == 0);
+  return 0;
+}