Commit c0f57472 authored by Gabriele Svelto's avatar Gabriele Svelto
Browse files

Bug 1752703 - Add interposers for functions manipulating the environment to... 

Bug 1752703 - Add interposers for functions manipulating the environment to prevent crashes r=glandium

This add interposers for getenv(), putenv(), setenv(), unsetenv() and
clearenv(). All interposers use a single lock for synchronization while
internally using the libc-provided functions. This is done to prevent races
that typically happen in Firefox code when multiple threads call getenv()
while others are changing variables using setenv() and putenv().

Differential Revision: https://phabricator.services.mozilla.com/D164471
parent 63bfefbb

mozglue/interposers/env_interposer.cpp

0 → 100644
+62 −0
Original line number Original line Diff line number Diff line 
/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */



#include <pthread.h>



#include "InterposerHelper.h"



// The interposers in this file cover all the functions used to access the

// environment (getenv(), putenv(), setenv(), unsetenv() and clearenv()). They

// all use the mutex below for synchronization to prevent races that caused

// startup crashes, see bug 1752703.

static pthread_mutex_t gEnvLock = PTHREAD_MUTEX_INITIALIZER;



extern "C" {



MFBT_API char* getenv(const char* name) {

  static const auto real_getenv = GET_REAL_SYMBOL(getenv);



  pthread_mutex_lock(&gEnvLock);

  char* result = real_getenv(name);

  pthread_mutex_unlock(&gEnvLock);

  return result;

}



MFBT_API int putenv(char* string) {

  static const auto real_putenv = GET_REAL_SYMBOL(putenv);



  pthread_mutex_lock(&gEnvLock);

  int result = real_putenv(string);

  pthread_mutex_unlock(&gEnvLock);

  return result;

}



MFBT_API int setenv(const char* name, const char* value, int replace) {

  static const auto real_setenv = GET_REAL_SYMBOL(setenv);



  pthread_mutex_lock(&gEnvLock);

  int result = real_setenv(name, value, replace);

  pthread_mutex_unlock(&gEnvLock);

  return result;

}



MFBT_API int unsetenv(const char* name) {

  static const auto real_unsetenv = GET_REAL_SYMBOL(unsetenv);



  pthread_mutex_lock(&gEnvLock);

  int result = real_unsetenv(name);

  pthread_mutex_unlock(&gEnvLock);

  return result;

}



MFBT_API int clearenv(void) {

  static const auto real_clearenv = GET_REAL_SYMBOL(clearenv);



  pthread_mutex_lock(&gEnvLock);

  int result = real_clearenv();

  pthread_mutex_unlock(&gEnvLock);

  return result;

}



}  // extern "C"

mozglue/interposers/moz.build

+4 −0
Original line number Original line Diff line number Diff line
@@ -7,6 +7,10 @@ Library("interposers") 




DEFINES["IMPL_MFBT"] = True

DEFINES["IMPL_MFBT"] = True





UNIFIED_SOURCES += [

    "env_interposer.cpp",

]



if CONFIG["MOZ_CRASHREPORTER"]:

if CONFIG["MOZ_CRASHREPORTER"]:

    UNIFIED_SOURCES += [

    UNIFIED_SOURCES += [

        "pthread_create_interposer.cpp",

        "pthread_create_interposer.cpp",