start-stop-daemon: use a pipe to sync parent/child processes
This fixes #557.
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@ -354,6 +354,9 @@ int main(int argc, char **argv)
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#ifdef PR_SET_NO_NEW_PRIVS
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bool no_new_privs = false;
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#endif
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int pipefd[2];
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char readbuf[1];
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ssize_t ss;
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applet = basename_c(argv[0]);
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atexit(cleanup);
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@ -864,12 +867,17 @@ int main(int argc, char **argv)
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if (background)
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signal_setup(SIGCHLD, handle_signal);
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/* Use a pipe to sync the parent/child processes. */
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if (pipe2(pipefd, O_CLOEXEC) == -1)
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eerrorx("%s: pipe2: %s", applet, strerror(errno));
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if ((pid = fork()) == -1)
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eerrorx("%s: fork: %s", applet, strerror(errno));
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/* Child process - lets go! */
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if (pid == 0) {
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pid_t mypid = getpid();
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close(pipefd[0]); /* Close the read end of the pipe. */
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umask(numask);
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#ifdef TIOCNOTTY
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@ -1097,7 +1105,8 @@ int main(int argc, char **argv)
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dup2(stderr_fd, STDERR_FILENO);
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for (i = getdtablesize() - 1; i >= 3; --i)
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close(i);
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if (i != pipefd[1])
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close(i);
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if (scheduler != NULL) {
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int scheduler_index;
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@ -1140,6 +1149,18 @@ int main(int argc, char **argv)
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}
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/* Parent process */
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close(pipefd[1]); /* Close the write end of the pipe. */
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/* The child never writes to the pipe, so this read will block until
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* the child calls exec or exits. */
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while ((ss = read(pipefd[0], readbuf, 1)) == -1 && errno == EINTR);
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if (ss == -1)
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eerrorx("%s: failed to read from pipe: %s",
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applet, strerror(errno));
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close(pipefd[0]);
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if (!background) {
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/* As we're not backgrounding the process, wait for our pid
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* to return */
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