[glibc] io: Implement lchmod using fchmodat [BZ #14578]

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6b89c385d8bd0700b25bac2c2d0bebe68d5cc05d

commit 6b89c385d8bd0700b25bac2c2d0bebe68d5cc05d
Author: Florian Weimer <fweimer@redhat.com>
Date:   Wed Jan 22 18:56:04 2020 +0100

    io: Implement lchmod using fchmodat [BZ #14578]

Diff:
---
 include/sys/stat.h                 |  1 +
 io/fchmodat.c                      |  1 +
 io/lchmod.c                        | 10 ++++------
 sysdeps/mach/hurd/fchmodat.c       |  1 +
 sysdeps/unix/sysv/linux/fchmodat.c |  1 +
 5 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/sys/stat.h b/include/sys/stat.h
index b82d452..92284ca 100644
--- a/include/sys/stat.h
+++ b/include/sys/stat.h
@@ -9,6 +9,7 @@ extern int __lstat (const char *__file, struct stat *__buf);
 extern int __chmod (const char *__file, __mode_t __mode);
 libc_hidden_proto (__chmod)
 extern int __fchmod (int __fd, __mode_t __mode);
+libc_hidden_proto (fchmodat)
 extern __mode_t __umask (__mode_t __mask);
 extern int __mkdir (const char *__path, __mode_t __mode);
 libc_hidden_proto (__mkdir)
diff --git a/io/fchmodat.c b/io/fchmodat.c
index 7f3a07a..78895ac 100644
--- a/io/fchmodat.c
+++ b/io/fchmodat.c
@@ -42,3 +42,4 @@ fchmodat (int fd, const char *file, mode_t mode, int flag)
   return -1;
 }
 stub_warning (fchmodat)
+libc_hidden_def (fchmodat)
diff --git a/io/lchmod.c b/io/lchmod.c
index 90b33a4..8b78803 100644
--- a/io/lchmod.c
+++ b/io/lchmod.c
@@ -1,4 +1,4 @@
-/* lchmod -- Change the protections of a file or symbolic link.  Stub version.
+/* lchmod -- Change the protections of a file or symbolic link.  Generic version.
    Copyright (C) 2002-2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -17,15 +17,13 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <errno.h>
-#include <sys/stat.h>
+#include <fcntl.h>
 #include <sys/types.h>
+#include <unistd.h>
 
 /* Change the protections of FILE to MODE.  */
 int
 lchmod (const char *file, mode_t mode)
 {
-  __set_errno (ENOSYS);
-  return -1;
+  return fchmodat (AT_FDCWD, file, mode, AT_SYMLINK_NOFOLLOW);
 }
-
-stub_warning (lchmod)
diff --git a/sysdeps/mach/hurd/fchmodat.c b/sysdeps/mach/hurd/fchmodat.c
index cd227d5..d42f952 100644
--- a/sysdeps/mach/hurd/fchmodat.c
+++ b/sysdeps/mach/hurd/fchmodat.c
@@ -37,3 +37,4 @@ fchmodat (int fd, const char *file, mode_t mode, int flag)
     return __hurd_fail (err);
   return 0;
 }
+libc_hidden_def (fchmodat)
diff --git a/sysdeps/unix/sysv/linux/fchmodat.c b/sysdeps/unix/sysv/linux/fchmodat.c
index 224439f..c41ebb2 100644
--- a/sysdeps/unix/sysv/linux/fchmodat.c
+++ b/sysdeps/unix/sysv/linux/fchmodat.c
@@ -38,3 +38,4 @@ fchmodat (int fd, const char *file, mode_t mode, int flag)
 
   return INLINE_SYSCALL (fchmodat, 3, fd, file, mode);
 }
+libc_hidden_def (fchmodat)