[PATCH 2/3] Linux: unlockpt needs to fail with EINVAL, not ENOTTY (bug 26053)

[Florian Weimer <fweimer@redhat.com>]

The EINVAL error code is mandated by POSIX and documented in the
manual.  Also clean up the unlockpt implementation a bit, assuming
that TIOCSPTLCK is always defined.

Enhance login/tst-grantpt to cover unlockpt corner cases.
---
 login/tst-grantpt.c                | 20 ++++++++++++++++----
 sysdeps/unix/sysv/linux/unlockpt.c | 21 +++++----------------
 2 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/login/tst-grantpt.c b/login/tst-grantpt.c
index 1d7a220fcf..8ca901ef94 100644
--- a/login/tst-grantpt.c
+++ b/login/tst-grantpt.c
@@ -1,4 +1,4 @@
-/* Test for grantpt error corner cases.
+/* Test for grantpt, unlockpt error corner cases.
    Copyright (C) 2001-2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -28,7 +28,7 @@
 #include <support/temp_file.h>
 #include <support/xunistd.h>
 
-/* Test grantpt with a closed descriptor.  */
+/* Test grantpt, unlockpt with a closed descriptor.  */
 static void
 test_ebadf (void)
 {
@@ -48,9 +48,12 @@ test_ebadf (void)
       printf ("grantpt(): expected: return = %d, errno = %d\n", -1, EBADF);
       printf ("           got: return = %d, errno = %d\n", ret, err);
     }
+
+  TEST_COMPARE (unlockpt (fd), -1);
+  TEST_COMPARE (errno, EBADF);
 }
 
-/* Test grantpt on a regular file.  */
+/* Test grantpt, unlockpt on a regular file.  */
 static void
 test_einval (void)
 {
@@ -68,10 +71,13 @@ test_einval (void)
       printf ("           got: return = %d, errno = %d\n", ret, err);
     }
 
+  TEST_COMPARE (unlockpt (fd), -1);
+  TEST_COMPARE (errno, EINVAL);
+
   xclose (fd);
 }
 
-/* Test grantpt on a non-ptmx pseudo-terminal.  */
+/* Test grantpt, unlockpt on a non-ptmx pseudo-terminal.  */
 static void
 test_not_ptmx (void)
 {
@@ -80,6 +86,9 @@ test_not_ptmx (void)
   TEST_COMPARE (grantpt (ptmx), 0);
   TEST_COMPARE (unlockpt (ptmx), 0);
 
+  /* A second unlock succeeds as well.  */
+  TEST_COMPARE (unlockpt (ptmx), 0);
+
   const char *name = ptsname (ptmx);
   TEST_VERIFY_EXIT (name != NULL);
   int pts = open (name, O_RDWR | O_NOCTTY);
@@ -88,6 +97,9 @@ test_not_ptmx (void)
   TEST_COMPARE (grantpt (pts), -1);
   TEST_COMPARE (errno, EINVAL);
 
+  TEST_COMPARE (unlockpt (pts), -1);
+  TEST_COMPARE (errno, EINVAL);
+
   xclose (pts);
   xclose (ptmx);
 }
diff --git a/sysdeps/unix/sysv/linux/unlockpt.c b/sysdeps/unix/sysv/linux/unlockpt.c
index 3a0ac7a96c..4d98abece0 100644
--- a/sysdeps/unix/sysv/linux/unlockpt.c
+++ b/sysdeps/unix/sysv/linux/unlockpt.c
@@ -27,22 +27,11 @@
 int
 unlockpt (int fd)
 {
-#ifdef TIOCSPTLCK
-  int save_errno = errno;
   int unlock = 0;
 
-  if (__ioctl (fd, TIOCSPTLCK, &unlock))
-    {
-      if (errno == EINVAL)
-	{
-	  __set_errno (save_errno);
-	  return 0;
-	}
-      else
-	return -1;
-    }
-#endif
-  /* If we have no TIOCSPTLCK ioctl, all slave pseudo terminals are
-     unlocked by default.  */
-  return 0;
+  int ret = __ioctl (fd, TIOCSPTLCK, &unlock);
+  if (ret != 0 && errno == ENOTTY)
+    /* POSIX mandates EINVAL for non-ptmx descriptors.  */
+    __set_errno (EINVAL);
+  return ret;
 }
-- 
2.26.2