libc/bionic/memory_mitigation_state.cpp

/*
 * Copyright (C) 2020 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "memory_mitigation_state.h"

#include <dirent.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdatomic.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <sys/types.h>

#include <bionic/mte.h>
#include <bionic/reserved_signals.h>

#include "private/ScopedRWLock.h"
#include "pthread_internal.h"

extern "C" void scudo_malloc_set_zero_contents(int zero_contents);
extern "C" void scudo_malloc_disable_memory_tagging();

#ifdef ANDROID_EXPERIMENTAL_MTE
static bool set_tcf_on_all_threads(int tcf) {
  static int g_tcf;
  g_tcf = tcf;

  return android_run_on_all_threads(
      [](void*) {
        int tagged_addr_ctrl = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
        if (tagged_addr_ctrl < 0) {
          return false;
        }

        tagged_addr_ctrl = (tagged_addr_ctrl & ~PR_MTE_TCF_MASK) | g_tcf;
        if (prctl(PR_SET_TAGGED_ADDR_CTRL, tagged_addr_ctrl, 0, 0, 0) < 0) {
          return false;
        }
        return true;
      },
      nullptr);
}
#endif

bool DisableMemoryMitigations(void* arg, size_t arg_size) {
  if (arg || arg_size) {
    return false;
  }

#ifdef USE_SCUDO
  scudo_malloc_set_zero_contents(0);

#ifdef ANDROID_EXPERIMENTAL_MTE
  if (mte_supported() && set_tcf_on_all_threads(PR_MTE_TCF_NONE)) {
    scudo_malloc_disable_memory_tagging();
  }
#endif
#endif

  return true;
}