1 files changed, 63 insertions, 0 deletions
diff --git a/io/tst-fchmod-errors.c b/io/tst-fchmod-errors.c
new file mode 100644
index 0000000000..bf2a4c568e
--- /dev/null
+++ b/io/tst-fchmod-errors.c
@@ -0,0 +1,63 @@
+/* Test various fchmod error cases.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+static int
+do_test (void)
+{
+  {
+    /* Permissions on /dev/null (the opened descriptor) cannot be changed.  */
+    int fd = xopen ("/dev/null", O_RDWR, 0);
+    if (getuid () == 0)
+      puts ("info: /dev/null fchmod test skipped because of root privileges");
+    else
+      {
+        errno = 0;
+        TEST_COMPARE (fchmod (fd, 0), -1);
+        TEST_COMPARE (errno, EPERM);
+      }
+    xclose (fd);
+
+    /* Now testing an invalid file descriptor.   */
+    errno = 0;
+    TEST_COMPARE (fchmod (fd, 0600), -1);
+    TEST_COMPARE (errno, EBADF);
+  }
+
+  errno = 0;
+  TEST_COMPARE (fchmod (-1, 0600), -1);
+  TEST_COMPARE (errno, EBADF);
+
+  errno = 0;
+  TEST_COMPARE (fchmod (AT_FDCWD, 0600), -1);
+  TEST_COMPARE (errno, EBADF);
+
+  /* Linux supports fchmod on pretty much all file descriptors, so
+     there is no check for failure on specific types of descriptors
+     here.  */
+
+  return 0;
+}
+
+#include <support/test-driver.c>