sandbox/linux/seccomp-bpf/die.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sandbox/linux/seccomp-bpf/die.h"
   6
   7 #include <errno.h>
   8 #include <signal.h>
   9 #include <stdio.h>
  10 #include <sys/prctl.h>
  11 #include <sys/syscall.h>
  12 #include <unistd.h>
  13
  14 #include <string>
  15
  16 #include "base/logging.h"
  17 #include "base/posix/eintr_wrapper.h"
  18 #include "sandbox/linux/seccomp-bpf/syscall.h"
  19
  20 namespace sandbox {
  21
  22 void Die::ExitGroup() {
  23   // exit_group() should exit our program. After all, it is defined as a
  24   // function that doesn't return. But things can theoretically go wrong.
  25   // Especially, since we are dealing with system call filters. Continuing
  26   // execution would be very bad in most cases where ExitGroup() gets called.
  27   // So, we'll try a few other strategies too.
  28   Syscall::Call(__NR_exit_group, 1);
  29
  30   // We have no idea what our run-time environment looks like. So, signal
  31   // handlers might or might not do the right thing. Try to reset settings
  32   // to a defined state; but we have not way to verify whether we actually
  33   // succeeded in doing so. Nonetheless, triggering a fatal signal could help
  34   // us terminate.
  35   signal(SIGSEGV, SIG_DFL);
  36   Syscall::Call(__NR_prctl, PR_SET_DUMPABLE, (void*)0, (void*)0, (void*)0);
  37   if (*(volatile char*)0) {
  38   }
  39
  40   // If there is no way for us to ask for the program to exit, the next
  41   // best thing we can do is to loop indefinitely. Maybe, somebody will notice
  42   // and file a bug...
  43   // We in fact retry the system call inside of our loop so that it will
  44   // stand out when somebody tries to diagnose the problem by using "strace".
  45   for (;;) {
  46     Syscall::Call(__NR_exit_group, 1);
  47   }
  48 }
  49
  50 void Die::SandboxDie(const char* msg, const char* file, int line) {
  51   if (simple_exit_) {
  52     LogToStderr(msg, file, line);
  53   } else {
  54     logging::LogMessage(file, line, logging::LOG_FATAL).stream() << msg;
  55   }
  56   ExitGroup();
  57 }
  58
  59 void Die::RawSandboxDie(const char* msg) {
  60   if (!msg)
  61     msg = "";
  62   RAW_LOG(FATAL, msg);
  63   ExitGroup();
  64 }
  65
  66 void Die::SandboxInfo(const char* msg, const char* file, int line) {
  67   if (!suppress_info_) {
  68     logging::LogMessage(file, line, logging::LOG_INFO).stream() << msg;
  69   }
  70 }
  71
  72 void Die::LogToStderr(const char* msg, const char* file, int line) {
  73   if (msg) {
  74     char buf[40];
  75     snprintf(buf, sizeof(buf), "%d", line);
  76     std::string s = std::string(file) + ":" + buf + ":" + msg + "\n";
  77
  78     // No need to loop. Short write()s are unlikely and if they happen we
  79     // probably prefer them over a loop that blocks.
  80     ignore_result(
  81         HANDLE_EINTR(Syscall::Call(__NR_write, 2, s.c_str(), s.length())));
  82   }
  83 }
  84
  85 bool Die::simple_exit_ = false;
  86 bool Die::suppress_info_ = false;
  87
  88 }  // namespace sandbox