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Paul Eggert 73dcdb9f30 Use faccessat, not access, when checking file permissions.
This fixes a bug that has been present in Emacs since its creation.
It was reported by Chris Torek in 1983 even before GNU Emacs existed,
which must set some sort of record.  (Torek's bug report was against
a predecessor of GNU Emacs, but GNU Emacs happened to have the
same common flaw.)  See Torek's Usenet posting
"setuid/setgid programs & Emacs" Article-I.D.: sri-arpa.858
Posted: Fri Apr  8 14:18:56 1983.
* .bzrignore: Add lib/fcntl.h.
* configure.ac (euidaccess): Remove check; gnulib does this for us now.
(gl_FCNTL_O_FLAGS): Define a dummy version.
* lib/at-func.c, lib/euidaccess.c, lib/faccessat.c, lib/fcntl.in.h:
* lib/getgroups.c, lib/group-member.c, lib/root-uid.h:
* lib/xalloc-oversized.h, m4/euidaccess.m4, m4/faccessat.m4:
* m4/fcntl_h.m4, m4/getgroups.m4, m4/group-member.m4:
New files, from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* admin/merge-gnulib (GNULIB_MODULES): Add faccessat.
(GNULIB_TOOL_FLAGS): Avoid at-internal, fchdir, malloc-posix,
openat-die, openat-h, save-cwd.  Do not avoid fcntl-h.
Omit gnulib's m4/fcntl-o.m4.
* nt/inc/ms-w32.h (AT_FDCWD, AT_EACCESS): New symbols.
(access): Remove.
(faccessat): New macro.
* src/Makefile.in (LIB_EACCESS): New macro.
(LIBES): Use it.
* src/callproc.c (init_callproc):
* src/charset.c (init_charset):
* src/fileio.c (check_existing, check_executable, check_writable)
(Ffile_readable_p):
* src/lread.c (openp, load_path_check):
* src/process.c (allocate_pty):
* src/xrdb.c (file_p):
Use effective UID when checking permissions, not real UID.
* src/callproc.c (init_callproc):
* src/charset.c (init_charset):
* src/lread.c (load_path_check, init_lread):
Test whether directories are accessible, not merely whether they exist.
* src/conf_post.h (GNULIB_SUPPORT_ONLY_AT_FDCWD): New macro.
* src/fileio.c (check_existing, check_executable, check_writable)
(Ffile_readable_p):
Use symbolic names instead of integers for the flags, as they're
portable now.
(check_writable): New arg AMODE.  All uses changed.
Set errno on failure.
(Ffile_readable_p): Use faccessat, not stat + open + close.
(Ffile_writable_p): No need to call check_existing + check_writable.
Just call check_writable and then look at errno.  This saves a syscall.
dir should never be nil; replace an unnecessary runtime check
with an eassert.  When checking the parent directory of a nonexistent
file, check that the directory is searchable as well as writable, as
we can't create files in unsearchable directories.
(file_directory_p): New function, which uses 'stat' on most platforms
but faccessat with D_OK (for efficiency) if WINDOWSNT.
(Ffile_directory_p, Fset_file_times): Use it.
(file_accessible_directory_p): New function, which uses a single
syscall for efficiency.
(Ffile_accessible_directory_p): Use it.
* src/xrdb.c (file_p): Use file_directory_p.
* src/lisp.h (file_directory_p, file_accessible_directory_p): New decls.
* src/lread.c (openp): When opening a file, use fstat rather than
stat, as that avoids a permissions race.  When not opening a file,
use file_directory_p rather than stat.
(dir_warning): First arg is now a usage string, not a format.
Use errno.  All uses changed.
* src/nsterm.m (ns_term_init): Remove unnecessary call to file-readable
that merely introduced a race.
* src/process.c, src/sysdep.c, src/term.c: All uses of '#ifdef O_NONBLOCK'
changed to '#if O_NONBLOCK', to accommodate gnulib O_* style,
and similarly for the other O_* flags.
* src/w32.c (sys_faccessat): Rename from sys_access and switch to
faccessat's API.  All uses changed.
* src/xrdb.c: Do not include <sys/stat.h>; no longer needed.
(magic_db): Rename from magic_file_p.
(magic_db, search_magic_path): Return an XrmDatabase rather than a
char *, so that we don't have to test for file existence
separately from opening the file for reading.  This removes a race
fixes a permission-checking problem, and simplifies the code.
All uses changed.
(file_p): Remove; no longer needed.

Fixes: debbugs:12632
2012-11-13 20:55:41 -08:00
..
icons Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
inc Use faccessat, not access, when checking file permissions. 2012-11-13 20:55:41 -08:00
.gitignore Nuke arch-tags. 2011-01-15 15:16:57 -08:00
addpm.c Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
addsection.c Support x64 build on MS-Windows with MSVC. 2012-09-30 23:36:42 +02:00
ChangeLog Use faccessat, not access, when checking file permissions. 2012-11-13 20:55:41 -08:00
cmdproxy.c Fix bug #10674 with infinite re-spawning of cmdproxy.exe. 2012-02-24 12:13:20 +02:00
config.nt nt/config.nt: Sync with autogen/config.in. 2012-11-05 15:30:32 +01:00
configure.bat Fix warnings when compiling on MS-Windows with -std=gnu99. 2012-10-17 21:02:44 +02:00
COPYING
ddeclient.c Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
emacs-src.tags Support TAGS targets in the w32 build. 2010-10-01 13:45:16 +02:00
emacs-x64.manifest Support x64 build on MS-Windows with MSVC. 2012-09-30 23:36:42 +02:00
emacs-x86.manifest Support x64 build on MS-Windows with MSVC. 2012-09-30 23:36:42 +02:00
emacs.rc Bump version to 24.3.50 2012-11-02 08:48:12 +08:00
emacsclient.rc Bump version to 24.3.50 2012-11-02 08:48:12 +08:00
envadd.bat Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
ftime-nostartup.bat Nuke arch-tags. 2011-01-15 15:16:57 -08:00
ftime.bat Nuke arch-tags. 2011-01-15 15:16:57 -08:00
gmake.defs Fix warnings when compiling on MS-Windows with -std=gnu99. 2012-10-17 21:02:44 +02:00
INSTALL Don't use the abbreviation "win" to refer to Windows (Bug#10421). 2012-07-29 01:18:29 -07:00
makefile.w32-in Bump version to 24.3.50 2012-11-02 08:48:12 +08:00
multi-install-info.bat Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
nmake.defs Support x64 build on MS-Windows with MSVC. 2012-09-30 23:36:42 +02:00
paths.h Fix bug #11959 with startup warnings on MS-Windows about ../site-lisp. 2012-08-04 17:17:10 +03:00
preprep.c Fix compilation warnings in the MS-Windows build. 2012-10-02 19:55:29 +02:00
README Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
README.W32 Support building on MS-Windows with libxml2. 2012-04-07 16:57:36 +03:00
runemacs.c Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00
subdirs.el
zipdist.bat Add 2012 to FSF copyright years for Emacs files 2012-01-05 01:46:05 -08:00

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	     Emacs for Windows NT/2000 and Windows 95/98/ME

  Copyright (C) 2001-2012  Free Software Foundation, Inc.
  See the end of the file for license conditions.

  This directory contains support for compiling and running GNU Emacs on
  Windows NT, Windows 95, and their successors.  This port supports all
  of the major functionality of the Unix version, including
  subprocesses, windowing features (fonts, colors, scroll bars, multiple
  frames, etc.), and networking support.

  Precompiled distributions are also available; ftp to

	ftp://ftp.gnu.org/gnu/emacs/windows/

  for the latest precompiled distributions.

* Building and installing

  See the INSTALL file in this directory for detailed instructions on
  building and installing Emacs on your system.

* EXE files produced

  Building and installing Emacs will produce the following executable
  files in the bin directory.

  + emacs.exe - The main Emacs executable. As this is designed to run
    as both a text-mode application (emacs -nw) and as a GUI application,
    it will pop up a command prompt window if run directly from Explorer.

  + runemacs.exe - A wrapper for running Emacs as a GUI application
    without popping up a command prompt window.

  + emacsclient.exe - A command-line client program that can
    communicate with a running Emacs process. See the `Emacs Server'
    node of the Emacs manual.

  + emacsclientw.exe - A version of emacsclient that does not open
    a command-line window.

  + addpm.exe - A basic installer that creates Start Menu icons for Emacs.
    Running this is optional.

  + cmdproxy.exe - Used internally by Emacs to work around problems with
    the native shells in various versions of Windows.

  + ctags.exe, etags.exe - Tools for generating tag files.  See the
  `Tags' node of the Emacs manual.

  + ebrowse.exe - A tool for generating C++ browse information.  See the
    `Ebrowse' manual.

  + ddeclient.exe - A tool for interacting with DDE servers.

  + hexl.exe - A tool for converting files to hex dumps.  See the
    `Editing Binary Files' node of the Emacs manual.

  + movemail.exe - A helper application for safely moving mail from
    a mail spool or POP server to a local user mailbox.  See the
    `Movemail' node of the Emacs manual.

* Further information

  There is a web page that serves as a FAQ for the Windows port of
  Emacs (a.k.a. NTEmacs) at:

	http://www.gnu.org/software/emacs/windows/ntemacs.html

  There is also a mailing list for discussing issues related to this
  port of Emacs.  For information about the list, see this Web page:

	http://mail.gnu.org/mailman/listinfo/help-emacs-windows

  To ask questions on the mailing list, send email to
  help-emacs-windows@gnu.org.  (You don't need to subscribe for that.)
  To subscribe to the list or unsubscribe from it, fill the form you
  find at http://mail.gnu.org/mailman/listinfo/help-emacs-windows as
  explained there.

  Another valuable source of information and help which should not be
  overlooked is the various Usenet news groups dedicated to Emacs.
  These are particularly good for help with general issues which aren't
  specific to the Windows port of Emacs.  The main news groups to use
  for seeking help are:

	gnu.emacs.help
	comp.emacs

  There are also fairly regular postings and announcements of new or
  updated Emacs packages on this group:

	gnu.emacs.sources

* Reporting bugs

  If you encounter a bug in this port of Emacs, we would like to hear
  about it.  First check the file etc/PROBLEMS and the FAQ on the web
  page above to see if the bug is already known and if there are any
  workarounds.  If not, then check whether the bug has something to do
  with code in your .emacs file, e.g. by invoking Emacs with the "-Q"
  option.

  Use the built in bug reporting functionality in Emacs so that it
  will be seen by the right people.  You can use the command M-x
  report-emacs-bug to create and send the bug report, but in some
  cases there is a function to report bugs in a specific package;
  e.g. M-x gnus-bug for Gnus, M-x c-submit-bug-report for C/C++/Java
  mode, etc.


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