int uv_spawn(uv_loop_t* loop, uv_process_t* process,
uv_process_options_t options) {
/*
* Save environ in the case that we get it clobbered
* by the child process.
*/
char** save_our_env = environ;
int stdin_pipe[2] = { -1, -1 };
int stdout_pipe[2] = { -1, -1 };
int stderr_pipe[2] = { -1, -1 };
#if SPAWN_WAIT_EXEC
int signal_pipe[2] = { -1, -1 };
struct pollfd pfd;
#endif
int status;
pid_t pid;
int flags;
uv__handle_init(loop, (uv_handle_t*)process, UV_PROCESS);
loop->counters.process_init++;
process->exit_cb = options.exit_cb;
if (options.stdin_stream &&
uv__process_init_pipe(options.stdin_stream, stdin_pipe, 0)) {
goto error;
}
if (options.stdout_stream &&
uv__process_init_pipe(options.stdout_stream, stdout_pipe, 0)) {
goto error;
}
if (options.stderr_stream &&
uv__process_init_pipe(options.stderr_stream, stderr_pipe, 0)) {
goto error;
}
/* This pipe is used by the parent to wait until
* the child has called `execve()`. We need this
* to avoid the following race condition:
*
* if ((pid = fork()) > 0) {
* kill(pid, SIGTERM);
* }
* else if (pid == 0) {
* execve("/bin/cat", argp, envp);
* }
*
* The parent sends a signal immediately after forking.
* Since the child may not have called `execve()` yet,
* there is no telling what process receives the signal,
* our fork or /bin/cat.
*
* To avoid ambiguity, we create a pipe with both ends
* marked close-on-exec. Then, after the call to `fork()`,
* the parent polls the read end until it sees POLLHUP.
*/
#if SPAWN_WAIT_EXEC
if (uv__make_pipe(signal_pipe, UV__F_NONBLOCK))
goto error;
#endif
pid = fork();
if (pid == -1) {
#if SPAWN_WAIT_EXEC
uv__close(signal_pipe[0]);
uv__close(signal_pipe[1]);
#endif
environ = save_our_env;
goto error;
}
if (pid == 0) {
if (stdin_pipe[0] >= 0) {
uv__close(stdin_pipe[1]);
dup2(stdin_pipe[0], STDIN_FILENO);
} else {
/* Reset flags that might be set by Node */
uv__cloexec(STDIN_FILENO, 0);
uv__nonblock(STDIN_FILENO, 0);
}
if (stdout_pipe[1] >= 0) {
uv__close(stdout_pipe[0]);
dup2(stdout_pipe[1], STDOUT_FILENO);
} else {
/* Reset flags that might be set by Node */
uv__cloexec(STDOUT_FILENO, 0);
uv__nonblock(STDOUT_FILENO, 0);
}
if (stderr_pipe[1] >= 0) {
uv__close(stderr_pipe[0]);
dup2(stderr_pipe[1], STDERR_FILENO);
} else {
/* Reset flags that might be set by Node */
uv__cloexec(STDERR_FILENO, 0);
uv__nonblock(STDERR_FILENO, 0);
}
if (options.cwd && chdir(options.cwd)) {
perror("chdir()");
_exit(127);
}
environ = options.env;
execvp(options.file, options.args);
perror("execvp()");
_exit(127);
/* Execution never reaches here. */
}
/* Parent. */
/* Restore environment. */
environ = save_our_env;
#if SPAWN_WAIT_EXEC
/* POLLHUP signals child has exited or execve()'d. */
uv__close(signal_pipe[1]);
do {
pfd.fd = signal_pipe[0];
pfd.events = POLLIN|POLLHUP;
pfd.revents = 0;
errno = 0, status = poll(&pfd, 1, -1);
}
while (status == -1 && (errno == EINTR || errno == ENOMEM));
assert((status == 1) && "poll() on pipe read end failed");
uv__close(signal_pipe[0]);
#endif
process->pid = pid;
ev_child_init(&process->child_watcher, uv__chld, pid, 0);
ev_child_start(process->loop->ev, &process->child_watcher);
process->child_watcher.data = process;
if (stdin_pipe[1] >= 0) {
assert(options.stdin_stream);
assert(stdin_pipe[0] >= 0);
uv__close(stdin_pipe[0]);
uv__nonblock(stdin_pipe[1], 1);
flags = UV_WRITABLE | (options.stdin_stream->ipc ? UV_READABLE : 0);
uv__stream_open((uv_stream_t*)options.stdin_stream, stdin_pipe[1],
flags);
}
if (stdout_pipe[0] >= 0) {
assert(options.stdout_stream);
assert(stdout_pipe[1] >= 0);
uv__close(stdout_pipe[1]);
uv__nonblock(stdout_pipe[0], 1);
flags = UV_READABLE | (options.stdout_stream->ipc ? UV_WRITABLE : 0);
uv__stream_open((uv_stream_t*)options.stdout_stream, stdout_pipe[0],
flags);
}
if (stderr_pipe[0] >= 0) {
assert(options.stderr_stream);
assert(stderr_pipe[1] >= 0);
uv__close(stderr_pipe[1]);
uv__nonblock(stderr_pipe[0], 1);
flags = UV_READABLE | (options.stderr_stream->ipc ? UV_WRITABLE : 0);
uv__stream_open((uv_stream_t*)options.stderr_stream, stderr_pipe[0],
flags);
}
return 0;
error:
uv__set_sys_error(process->loop, errno);
uv__close(stdin_pipe[0]);
uv__close(stdin_pipe[1]);
uv__close(stdout_pipe[0]);
uv__close(stdout_pipe[1]);
uv__close(stderr_pipe[0]);
uv__close(stderr_pipe[1]);
return -1;
}
static void uv__process_child_init(const uv_process_options_t* options,
int stdio_count,
int (*pipes)[2],
int error_fd) {
int close_fd;
int use_fd;
int fd;
if (options->flags & UV_PROCESS_DETACHED)
setsid();
/* First duplicate low numbered fds, since it's not safe to duplicate them,
* they could get replaced. Example: swapping stdout and stderr; without
* this fd 2 (stderr) would be duplicated into fd 1, thus making both
* stdout and stderr go to the same fd, which was not the intention. */
for (fd = 0; fd < stdio_count; fd++) {
use_fd = pipes[fd][1];
if (use_fd < 0 || use_fd >= fd)
continue;
pipes[fd][1] = fcntl(use_fd, F_DUPFD, stdio_count);
if (pipes[fd][1] == -1) {
uv__write_int(error_fd, -errno);
_exit(127);
}
}
for (fd = 0; fd < stdio_count; fd++) {
close_fd = pipes[fd][0];
use_fd = pipes[fd][1];
if (use_fd < 0) {
if (fd >= 3)
continue;
else {
/* redirect stdin, stdout and stderr to /dev/null even if UV_IGNORE is
* set
*/
use_fd = open("/dev/null", fd == 0 ? O_RDONLY : O_RDWR);
close_fd = use_fd;
if (use_fd == -1) {
uv__write_int(error_fd, -errno);
_exit(127);
}
}
}
if (fd == use_fd)
uv__cloexec(use_fd, 0);
else
fd = dup2(use_fd, fd);
if (fd == -1) {
uv__write_int(error_fd, -errno);
_exit(127);
}
if (fd <= 2)
uv__nonblock(fd, 0);
if (close_fd >= stdio_count)
uv__close(close_fd);
}
for (fd = 0; fd < stdio_count; fd++) {
use_fd = pipes[fd][1];
if (use_fd >= stdio_count)
uv__close(use_fd);
}
if (options->cwd != NULL && chdir(options->cwd)) {
uv__write_int(error_fd, -errno);
_exit(127);
}
if (options->flags & (UV_PROCESS_SETUID | UV_PROCESS_SETGID)) {
/* When dropping privileges from root, the `setgroups` call will
* remove any extraneous groups. If we don't call this, then
* even though our uid has dropped, we may still have groups
* that enable us to do super-user things. This will fail if we
* aren't root, so don't bother checking the return value, this
* is just done as an optimistic privilege dropping function.
*/
SAVE_ERRNO(setgroups(0, NULL));
}
if ((options->flags & UV_PROCESS_SETGID) && setgid(options->gid)) {
uv__write_int(error_fd, -errno);
_exit(127);
}
if ((options->flags & UV_PROCESS_SETUID) && setuid(options->uid)) {
uv__write_int(error_fd, -errno);
_exit(127);
}
if (options->env != NULL) {
environ = options->env;
}
execvp(options->file, options->args);
uv__write_int(error_fd, -errno);
_exit(127);
}
