>From 4647a343f5e6c903495fa01a50743af5015552a6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Va=C5=A1=C3=ADk?= <address@hidden>
Date: Mon, 5 Mar 2012 14:43:39 +0100
Subject: [PATCH] chmod: Clear special bits for octal modes with 5+ digits or preceeded by @.
         * NEWS: Mention the changes.
         * doc/perm.texi (Directory Setuid and Setgid) : Document changes.
         * tests/chmod/setuid : Check the new behaviour by test.
         Suggested by Eric Blake.

---
 NEWS               |    4 ++++
 doc/perm.texi      |   26 +++++++++++++++++++++++---
 tests/chmod/setgid |   24 ++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/NEWS b/NEWS
index 8006669..c0657e2 100644
--- a/NEWS
+++ b/NEWS
@@ -16,6 +16,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   split now accepts the --additional-suffix option, to append an
   additional static suffix to output file names.
 
+  chmod, mkdir, install now accept new style of octal mode specification.
+  When octal mode is preceeded by @ or is 5+ digits long with leading zeros,
+  it can clear the set user id and set group id bits on directories.
+
 ** Bug fixes
 
   mv now lets you move a symlink onto a same-inode destination file that
diff --git a/doc/perm.texi b/doc/perm.texi
index 84f8500..d1469a9 100644
--- a/doc/perm.texi
+++ b/doc/perm.texi
@@ -495,7 +495,10 @@ alternative to giving a symbolic mode, you can give an octal (base 8)
 number that represents the mode.
 This number is always interpreted in octal; you do not have to add a
 leading @samp{0}, as you do in C.  Mode @samp{0055} is the same as
-mode @samp{55}.
+mode @samp{55}. However, adding leading zeros to create octal number with
+at least 5 digits means that this mode is taken explicitly - so could
+clear even the set-user-ID and set-group-ID bits of directories. The
+same could be enforced by preceeding the numeric mode by "@@" character.
 
 A numeric mode is usually shorter than the corresponding symbolic
 mode, but it is limited in that normally it cannot take into account the
@@ -559,8 +562,11 @@ bits of directories.  If commands like @command{chmod} and
 mechanisms would be less convenient and it would be harder to share
 files.  Therefore, a command like @command{chmod} does not affect the
 set-user-ID or set-group-ID bits of a directory unless the user
-specifically mentions them in a symbolic mode, or sets them in
-a numeric mode.  For example, on systems that support
+specifically mentions them in a symbolic mode, explicitly enforces the
+mode by using "@@" character before numeric mode or by at least 5 digits
+long octal mode,or when sets them in a numeric mode.
+
+For example, on systems that support
 set-group-ID inheritance:
 
 @example
@@ -598,6 +604,20 @@ explicitly in a symbolic mode, e.g.:
 chmod a-s D
 @end example
 
+If you want force the chmod to change directory mode to exact numeric mode
+(clear the special bits), you could use at least 5 digit octal mode
+or preceed the mode with "@@" character, e.g.:
+
address@hidden
+# These commands try to clear the set-user-ID
+# and set-group-ID bits of directories D and E and set
+# their permissions to 0755.
+mkdir D E
+chmod 6755 D E
+chmod 00755 D
+chmod @@755 E
address@hidden example
+
 This behavior is a @acronym{GNU} extension.  Portable scripts should
 not rely on requests to set or clear these bits on directories, as
 @acronym{POSIX} allows implementations to ignore these requests.
diff --git a/tests/chmod/setgid b/tests/chmod/setgid
index eaa9351..6db6794 100755
--- a/tests/chmod/setgid
+++ b/tests/chmod/setgid
@@ -45,4 +45,28 @@ chmod 755 d
 
 case `ls -ld d` in drwxr-sr-x*);; *) fail=1;; esac
 
+# make sure that it doesn't clear the special bits for 4 digit octal mode
+chmod 0755 d
+case `ls -ld d` in drwxr-sr-x*);; *) fail=1;; esac
+
+# make sure that it doesn't clear the special bits for 4 digit octal mode
+# with two leading zeros
+chmod 0055 d
+case `ls -ld d` in d---r-sr-x*);; *) fail=1;; esac
+
+# make sure that it clears the special bits for 5 digit octal mode with
+# leading zero
+chmod 00755 d
+case `ls -ld d` in drwxr-xr-x*);; *) fail=1;; esac
+
+# make sure that it clears the special bits even for more leading zeros
+# octal digits
+chmod 00000755 d
+case `ls -ld d` in drwxr-xr-x*);; *) fail=1;; esac
+
+# make sure that it clears the special bits even for exact mode(@)
+chmod @755 d
+case `ls -ld d` in drwxr-xr-x*);; *) fail=1;; esac
+
+
 Exit $fail
-- 
1.7.1