[Bug libc/6712] New: Race condition in calling setlocale()

["sharyathi at in dot ibm dot com" <sourceware-bugzilla at sourceware dot org>]

Description

During PHP engine development it was observed that a thread calling
strcmp() would crash if another thread was also calling setlocale().
The problem is difficult to reproduce, but the following is a
line-by-line analysis of where the race condition exists.
-----------------------------------------------------------------------
char *
setlocale (int category, const char *locale)
{
  char *locale_path;
  .......
 /* Does user want name of current locale?  */
  if (locale == NULL)
    return (char *) _nl_global_locale.__names[category];

  if (strcmp (locale, _nl_global_locale.__names[category]) == 0)
<== SIGSEGVs while accessing _nl_global_locale

  ..........


if (category == LC_ALL)
    {
  ..........
/* Protect global data.  */
      __libc_rwlock_wrlock (__libc_setlocale_lock);
  ..........
setname (LC_ALL, composite)
<== Frees the global variable _nl_global_locale.__names[category]

..........
 /* Critical section left.  */
      __libc_rwlock_unlock (__libc_setlocale_lock);
} //category == LC_ALL

  ..........


} //setlocale end of function
-----------------------------------------------------------------------
Though setlocale() is not on the POSIX.1 list of async-signal safe
functions as in section 2.4.3
http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html#tag_02_04

It still needs to be thread safe according to section 2.9.1 in
http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html

-- 
           Summary: Race condition in calling setlocale()
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: sharyathi at in dot ibm dot com
                CC: bmark at us dot ibm dot com,glibc-bugs at sources dot
                    redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=6712

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