Add thread safety to some environment accesses

The previous commit added a mutex specifically for protecting against
simultaneous accesses of the environment.  This commit changes the
normal getenv, putenv, and clearenv functions to use it, to avoid races.

This makes the code simpler in places where we've gotten burned and
added stuff to avoid races.  Other places where we haven't known we were
getting burned could have existed until now.  Now that comes
automatically, and we can remove the special cases we earlier stumbled
over.

getenv() returns a pointer to static memory, which can be overwritten at
any moment from another thread, or even another getenv from the same
thread.  This commit changes the accesses to be under control of a
mutex, and in the case of getenv, a mortalized copy is created so that
there is no possible race.

1 files changed, 4 insertions, 26 deletions

diff --git a/locale.c b/locale.c
index d68ef50e1b..bffb8124c8 100644
--- a/locale.c
+++ b/locale.c
@@ -791,16 +791,6 @@ S_emulate_setlocale(const int category,
             if (! default_name || strEQ(default_name, "")) {
                 default_name = "C";
             }
-            else if (PL_scopestack_ix != 0) {
-                /* To minimize other threads messing with the environment,
-                 * we copy the variable, making it a temporary.  But this
-                 * doesn't work upon program initialization before any
-                 * scopes are created, and at this time, there's nothing
-                 * else going on that would interfere.  So skip the copy
-                 * in that case */
-                default_name = savepv(default_name);
-                SAVEFREEPV(default_name);
-            }
 
             if (category != LC_ALL) {
                 const char * const name = PerlEnv_getenv(category_names[index]);
@@ -835,22 +825,19 @@ S_emulate_setlocale(const int category,
 
                 for (i = 0; i < LC_ALL_INDEX; i++) {
                     const char * const env_override
-                                    = savepv(PerlEnv_getenv(category_names[i]));
+                                            = PerlEnv_getenv(category_names[i]);
                     const char * this_locale = (   env_override
                                                 && strNE(env_override, ""))
                                                ? env_override
                                                : default_name;
                     if (! emulate_setlocale(categories[i], this_locale, i, TRUE))
                     {
-                        Safefree(env_override);
                         return NULL;
                     }
 
                     if (strNE(this_locale, default_name)) {
                         did_override = TRUE;
                     }
-
-                    Safefree(env_override);
                 }
 
                 /* If all the categories are the same, we can set LC_ALL to
@@ -3310,7 +3297,7 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
 #else  /* USE_LOCALE */
 #  ifdef __GLIBC__
 
-    const char * const language   = savepv(PerlEnv_getenv("LANGUAGE"));
+    const char * const language = PerlEnv_getenv("LANGUAGE");
 
 #  endif
 
@@ -3320,8 +3307,8 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
                                         : "";
     const char* trial_locales[5];   /* 5 = 1 each for "", LC_ALL, LANG, "", C */
     unsigned int trial_locales_count;
-    const char * const lc_all     = savepv(PerlEnv_getenv("LC_ALL"));
-    const char * const lang       = savepv(PerlEnv_getenv("LANG"));
+    const char * const lc_all     = PerlEnv_getenv("LC_ALL");
+    const char * const lang       = PerlEnv_getenv("LANG");
     bool setlocale_failure = FALSE;
     unsigned int i;
 
@@ -3909,15 +3896,6 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
     }
 
 #  endif
-#  ifdef __GLIBC__
-
-    Safefree(language);
-
-#  endif
-
-    Safefree(lc_all);
-    Safefree(lang);
-
 #endif /* USE_LOCALE */
 #ifdef DEBUGGING