1// Copyright 2013 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/services/init_process_reaper.h"
6
7#include <signal.h>
8#include <string.h>
9#include <sys/socket.h>
10#include <sys/types.h>
11#include <sys/wait.h>
12#include <unistd.h>
13
14#include "base/callback.h"
15#include "base/logging.h"
16#include "base/posix/eintr_wrapper.h"
17
18namespace sandbox {
19
20namespace {
21
22void DoNothingSignalHandler(int signal) {}
23
24}  // namespace
25
26bool CreateInitProcessReaper(base::Closure* post_fork_parent_callback) {
27  int sync_fds[2];
28  // We want to use send, so we can't use a pipe
29  if (socketpair(AF_UNIX, SOCK_STREAM, 0, sync_fds)) {
30    PLOG(ERROR) << "Failed to create socketpair";
31    return false;
32  }
33  pid_t child_pid = fork();
34  if (child_pid == -1) {
35    int close_ret;
36    close_ret = IGNORE_EINTR(close(sync_fds[0]));
37    DPCHECK(!close_ret);
38    close_ret = IGNORE_EINTR(close(sync_fds[1]));
39    DPCHECK(!close_ret);
40    return false;
41  }
42  if (child_pid) {
43    // In the parent, assuming the role of an init process.
44    // The disposition for SIGCHLD cannot be SIG_IGN or wait() will only return
45    // once all of our childs are dead. Since we're init we need to reap childs
46    // as they come.
47    struct sigaction action;
48    memset(&action, 0, sizeof(action));
49    action.sa_handler = &DoNothingSignalHandler;
50    CHECK(sigaction(SIGCHLD, &action, NULL) == 0);
51
52    int close_ret;
53    close_ret = IGNORE_EINTR(close(sync_fds[0]));
54    DPCHECK(!close_ret);
55    close_ret = shutdown(sync_fds[1], SHUT_RD);
56    DPCHECK(!close_ret);
57    if (post_fork_parent_callback)
58      post_fork_parent_callback->Run();
59    // Tell the child to continue
60    CHECK(HANDLE_EINTR(send(sync_fds[1], "C", 1, MSG_NOSIGNAL)) == 1);
61    close_ret = IGNORE_EINTR(close(sync_fds[1]));
62    DPCHECK(!close_ret);
63
64    for (;;) {
65      // Loop until we have reaped our one natural child
66      siginfo_t reaped_child_info;
67      int wait_ret =
68          HANDLE_EINTR(waitid(P_ALL, 0, &reaped_child_info, WEXITED));
69      if (wait_ret)
70        _exit(1);
71      if (reaped_child_info.si_pid == child_pid) {
72        int exit_code = 0;
73        // We're done waiting
74        if (reaped_child_info.si_code == CLD_EXITED) {
75          exit_code = reaped_child_info.si_status;
76        }
77        // Exit with the same exit code as our parent. Exit with 0 if we got
78        // signaled.
79        _exit(exit_code);
80      }
81    }
82  } else {
83    // The child needs to wait for the parent to run the callback to avoid a
84    // race condition.
85    int close_ret;
86    close_ret = IGNORE_EINTR(close(sync_fds[1]));
87    DPCHECK(!close_ret);
88    close_ret = shutdown(sync_fds[0], SHUT_WR);
89    DPCHECK(!close_ret);
90    char should_continue;
91    int read_ret = HANDLE_EINTR(read(sync_fds[0], &should_continue, 1));
92    close_ret = IGNORE_EINTR(close(sync_fds[0]));
93    DPCHECK(!close_ret);
94    if (read_ret == 1)
95      return true;
96    else
97      return false;
98  }
99}
100
101}  // namespace sandbox.
102