[Bug libc/12685] New: fopen doesn't last byte of valid modes

[Bug libc/12685] New: fopen doesn't last byte of valid modes

[eblake at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

           Summary: fopen doesn't last byte of valid modes
           Product: glibc
           Version: 2.13
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: eblake@redhat.com


$ cat foo.c
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>

int main (void)
{
  FILE *f = fopen ("/dev/null", "rb+cmxe");
  if (!f) exit (1);
  int fd = fileno (f);
  if (fd < 0) exit (2);
  int mode = fcntl (fd, F_GETFD);
  if (mode < 0) exit (3);
  return !(mode & FD_CLOEXEC);
}
$ ./foo; echo $?
1

Oops - an off-by-one error in fileops.c ended up ignoring 'e'.  The same goes
for any other valid byte that doesn't appear until mode[6].

diff --git i/libio/fileops.c w/libio/fileops.c
index 4698953..ee6ce13 100644
--- i/libio/fileops.c
+++ w/libio/fileops.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1993, 1995, 1997-2005, 2006, 2007, 2008, 2009
+/* Copyright (C) 1993, 1995, 1997-2005, 2006, 2007, 2008, 2009, 2011
    Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Written by Per Bothner <bothner@cygnus.com>.
@@ -290,7 +290,7 @@ _IO_new_file_fopen (fp, filename, mode, is32not64)
 #ifdef _LIBC
   last_recognized = mode;
 #endif
-  for (i = 1; i < 6; ++i)
+  for (i = 1; i < 7; ++i)
     {
       switch (*++mode)
     {

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[eblake at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Eric Blake <eblake at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|fopen doesn't last byte of  |fopen doesn't honor last
                   |valid modes                 |byte of valid modes

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[ppluzhnikov at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppluzhnikov at google dot
                   |                            |com

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Ulrich Drepper <drepper.fsp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #1 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-04-23 03:41:46 UTC ---
The patch didn't apply.  I did it manually.

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[mtk.manpages at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Michael Kerrisk <mtk.manpages at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |mtk.manpages at gmail dot
                   |                            |com
         Resolution|FIXED                       |

--- Comment #2 from Michael Kerrisk <mtk.manpages at gmail dot com> 2012-04-22 01:58:14 UTC ---
Actually, is there any reason at all to limit the length of the string? Whay
not parse until NUL? Given that "mode" may be a constructed string, or that
other flags may be added in the future, it seems that arbitrarily limiting the
length of the string to some number of bytes is just setting up both glibc and
userspace bugs for the future.

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[mtk.manpages at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

--- Comment #3 from Michael Kerrisk <mtk.manpages at gmail dot com> 2012-04-22 02:01:46 UTC ---
A similar remark applies for fdopen(), which uses different code for parsing
'mode'.

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[Bug libc/12685] fopen doesn't honor last byte of valid modes

[mtk.manpages at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

--- Comment #4 from Michael Kerrisk <mtk.manpages at gmail dot com> 2012-04-22 02:11:48 UTC ---
Sorry, my original comment should have read:

Actually, is there any reason at all to limit the length of the string? Why
not parse until NUL *or comma*? Given that "mode" may be a constructed string,
or that other flags may be added in the future, it seems that arbitrarily
limiting the length of the string to some number of bytes is just setting up
both glibc and userspace bugs for the future.

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[Bug stdio/12685] fopen doesn't honor last byte of valid modes

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libc                        |stdio
         AssignedTo|drepper.fsp at gmail dot    |unassigned at sourceware
                   |com                         |dot org

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[Bug stdio/12685] fopen doesn't honor last byte of valid modes

[ondra at iuuk dot mff.cuni.cz]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

OndrejBilka <ondra at iuuk dot mff.cuni.cz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ondra at iuuk dot
                   |                            |mff.cuni.cz

--- Comment #5 from OndrejBilka <ondra at iuuk dot mff.cuni.cz> 2013-05-09 15:13:53 UTC ---
Could you specify why do you want comma as terminator?

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[Bug stdio/12685] fopen doesn't honor last byte of valid modes

[bugdal at aerifal dot cx]

http://sourceware.org/bugzilla/show_bug.cgi?id=12685

Rich Felker <bugdal at aerifal dot cx> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugdal at aerifal dot cx

--- Comment #6 from Rich Felker <bugdal at aerifal dot cx> 2013-05-09 16:08:22 UTC ---
I believe it's to ignore some non-standard syntax certain implementations use
for binding a non-default character encoding at open time. I recall seeing such
a usage before but I can't think where.

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[Bug stdio/12685] fopen doesn't honor last byte of valid modes

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=12685

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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