1 files changed, 34 insertions, 50 deletions

diff --git a/lib/lchmod.c b/lib/lchmod.c
index 706dddff7bb..8410a2d835f 100644
--- a/lib/lchmod.c
+++ b/lib/lchmod.c
@@ -25,17 +25,9 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 
-#ifdef __osf__
-/* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
-   eliminates this include because of the preliminary #include <sys/stat.h>
-   above.  */
-# include "sys/stat.h"
-#else
-# include <sys/stat.h>
-#endif
-
 #include <intprops.h>
 
 /* Work like chmod, except when FILE is a symbolic link.
@@ -45,7 +37,9 @@
 int
 lchmod (char const *file, mode_t mode)
 {
-#if defined O_PATH && defined AT_EMPTY_PATH
+  char readlink_buf[1];
+
+#ifdef O_PATH
   /* Open a file descriptor with O_NOFOLLOW, to make sure we don't
      follow symbolic links, if /proc is mounted.  O_PATH is used to
      avoid a failure if the file is not readable.
@@ -54,56 +48,46 @@ lchmod (char const *file, mode_t mode)
   if (fd < 0)
     return fd;
 
-  /* Up to Linux 5.3 at least, when FILE refers to a symbolic link, the
-     chmod call below will change the permissions of the symbolic link
-     - which is undesired - and on many file systems (ext4, btrfs, jfs,
-     xfs, ..., but not reiserfs) fail with error EOPNOTSUPP - which is
-     misleading.  Therefore test for a symbolic link explicitly.
-     Use fstatat because fstat does not work on O_PATH descriptors
-     before Linux 3.6.  */
-  struct stat st;
-  if (fstatat (fd, "", &st, AT_EMPTY_PATH) != 0)
+  int err;
+  if (0 <= readlinkat (fd, "", readlink_buf, sizeof readlink_buf))
+    err = EOPNOTSUPP;
+  else if (errno == EINVAL)
     {
-      int stat_errno = errno;
-      close (fd);
-      errno = stat_errno;
-      return -1;
-    }
-  if (S_ISLNK (st.st_mode))
-    {
-      close (fd);
-      errno = EOPNOTSUPP;
-      return -1;
+      static char const fmt[] = "/proc/self/fd/%d";
+      char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
+      sprintf (buf, fmt, fd);
+      err = chmod (buf, mode) == 0 ? 0 : errno == ENOENT ? -1 : errno;
     }
+  else
+    err = errno == ENOENT ? -1 : errno;
 
-# if defined __linux__ || defined __ANDROID__ || defined __CYGWIN__
-  static char const fmt[] = "/proc/self/fd/%d";
-  char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
-  sprintf (buf, fmt, fd);
-  int chmod_result = chmod (buf, mode);
-  int chmod_errno = errno;
   close (fd);
-  if (chmod_result == 0)
-    return chmod_result;
-  if (chmod_errno != ENOENT)
+
+  errno = err;
+  if (0 <= err)
+    return err == 0 ? 0 : -1;
+#endif
+
+  size_t len = strlen (file);
+  if (len && file[len - 1] == '/')
     {
-      errno = chmod_errno;
-      return chmod_result;
+      struct stat st;
+      if (lstat (file, &st) < 0)
+        return -1;
+      if (!S_ISDIR (st.st_mode))
+        {
+          errno = ENOTDIR;
+          return -1;
+        }
     }
-# endif
-  /* /proc is not mounted or would not work as in GNU/Linux.  */
-
-#elif HAVE_LSTAT
-  struct stat st;
-  int lstat_result = lstat (file, &st);
-  if (lstat_result != 0)
-    return lstat_result;
-  if (S_ISLNK (st.st_mode))
+
+  /* O_PATH + /proc is not supported.  */
+
+  if (0 <= readlink (file, readlink_buf, sizeof readlink_buf))
     {
       errno = EOPNOTSUPP;
       return -1;
     }
-#endif
 
   /* Fall back on chmod, despite a possible race.  */
   return chmod (file, mode);