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 "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
  13 #include "sandbox/linux/seccomp-bpf/syscall.h"
  14
  15
  16 namespace playground2 {
  17
  18 void Die::ExitGroup() {
  19   // exit_group() should exit our program. After all, it is defined as a
  20   // function that doesn't return. But things can theoretically go wrong.
  21   // Especially, since we are dealing with system call filters. Continuing
  22   // execution would be very bad in most cases where ExitGroup() gets called.
  23   // So, we'll try a few other strategies too.
  24   SandboxSyscall(__NR_exit_group, 1);
  25
  26   // We have no idea what our run-time environment looks like. So, signal
  27   // handlers might or might not do the right thing. Try to reset settings
  28   // to a defined state; but we have not way to verify whether we actually
  29   // succeeded in doing so. Nonetheless, triggering a fatal signal could help
  30   // us terminate.
  31   signal(SIGSEGV, SIG_DFL);
  32   SandboxSyscall(__NR_prctl, PR_SET_DUMPABLE, (void *)0, (void *)0, (void *)0);
  33   if (*(volatile char *)0) { }
  34
  35   // If there is no way for us to ask for the program to exit, the next
  36   // best thing we can do is to loop indefinitely. Maybe, somebody will notice
  37   // and file a bug...
  38   // We in fact retry the system call inside of our loop so that it will
  39   // stand out when somebody tries to diagnose the problem by using "strace".
  40   for (;;) {
  41     SandboxSyscall(__NR_exit_group, 1);
  42   }
  43 }
  44
  45 void Die::SandboxDie(const char *msg, const char *file, int line) {
  46   if (simple_exit_) {
  47     LogToStderr(msg, file, line);
  48   } else {
  49     #if defined(SECCOMP_BPF_STANDALONE)
  50       Die::LogToStderr(msg, file, line);
  51     #else
  52       logging::LogMessage(file, line, logging::LOG_FATAL).stream() << msg;
  53     #endif
  54   }
  55   ExitGroup();
  56 }
  57
  58 void Die::SandboxInfo(const char *msg, const char *file, int line) {
  59   if (!suppress_info_) {
  60   #if defined(SECCOMP_BPF_STANDALONE)
  61     Die::LogToStderr(msg, file, line);
  62   #else
  63     logging::LogMessage(file, line, logging::LOG_INFO).stream() << msg;
  64   #endif
  65   }
  66 }
  67
  68 void Die::LogToStderr(const char *msg, const char *file, int line) {
  69   if (msg) {
  70     char buf[40];
  71     snprintf(buf, sizeof(buf), "%d", line);
  72     std::string s = std::string(file) + ":" + buf + ":" + msg + "\n";
  73
  74     // No need to loop. Short write()s are unlikely and if they happen we
  75     // probably prefer them over a loop that blocks.
  76     if (HANDLE_EINTR(SandboxSyscall(__NR_write, 2, s.c_str(), s.length()))) { }
  77   }
  78 }
  79
  80 bool Die::simple_exit_   = false;
  81 bool Die::suppress_info_ = false;
  82
  83 }  // namespace