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