static int
make_inheritable(PyObject *py_fds_to_keep, int errpipe_write)
{
Py_ssize_t i, len;
len = PySequence_Length(py_fds_to_keep);
for (i = 0; i < len; ++i) {
PyObject* fdobj = PySequence_Fast_GET_ITEM(py_fds_to_keep, i);
long fd = PyLong_AsLong(fdobj);
assert(!PyErr_Occurred());
assert(0 <= fd && fd <= INT_MAX);
if (fd == errpipe_write) {
/* errpipe_write is part of py_fds_to_keep. It must be closed at
exec(), but kept open in the child process until exec() is
called. */
continue;
}
if (_Py_set_inheritable((int)fd, 1, NULL) < 0)
return -1;
}
return 0;
}
/* Duplicate a file descriptor. The new file descriptor is created as
non-inheritable. Return a new file descriptor on success, raise an OSError
exception and return -1 on error.
The GIL is released to call dup(). The caller must hold the GIL. */
int
_Py_dup(int fd)
{
#ifdef MS_WINDOWS
HANDLE handle;
DWORD ftype;
#endif
if (!_PyVerify_fd(fd)) {
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
#ifdef MS_WINDOWS
handle = (HANDLE)_get_osfhandle(fd);
if (handle == INVALID_HANDLE_VALUE) {
PyErr_SetFromWindowsErr(0);
return -1;
}
/* get the file type, ignore the error if it failed */
ftype = GetFileType(handle);
Py_BEGIN_ALLOW_THREADS
fd = dup(fd);
Py_END_ALLOW_THREADS
if (fd < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
/* Character files like console cannot be make non-inheritable */
if (ftype != FILE_TYPE_CHAR) {
if (_Py_set_inheritable(fd, 0, NULL) < 0) {
close(fd);
return -1;
}
}
#elif defined(HAVE_FCNTL_H) && defined(F_DUPFD_CLOEXEC)
Py_BEGIN_ALLOW_THREADS
fd = fcntl(fd, F_DUPFD_CLOEXEC, 0);
Py_END_ALLOW_THREADS
if (fd < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
#else
Py_BEGIN_ALLOW_THREADS
fd = dup(fd);
Py_END_ALLOW_THREADS
if (fd < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
if (_Py_set_inheritable(fd, 0, NULL) < 0) {
close(fd);
return -1;
}
#endif
return fd;
}
/*
* This function is code executed in the child process immediately after fork
* to set things up and call exec().
*
* All of the code in this function must only use async-signal-safe functions,
* listed at `man 7 signal` or
* http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
*
* This restriction is documented at
* http://www.opengroup.org/onlinepubs/009695399/functions/fork.html.
*/
static void
child_exec(char *const exec_array[],
char *const argv[],
char *const envp[],
const char *cwd,
int p2cread, int p2cwrite,
int c2pread, int c2pwrite,
int errread, int errwrite,
int errpipe_read, int errpipe_write,
int close_fds, int restore_signals,
int call_setsid,
PyObject *py_fds_to_keep,
PyObject *preexec_fn,
PyObject *preexec_fn_args_tuple)
{
int i, saved_errno, reached_preexec = 0;
PyObject *result;
const char* err_msg = "";
/* Buffer large enough to hold a hex integer. We can't malloc. */
char hex_errno[sizeof(saved_errno)*2+1];
if (make_inheritable(py_fds_to_keep, errpipe_write) < 0)
goto error;
/* Close parent's pipe ends. */
if (p2cwrite != -1)
POSIX_CALL(close(p2cwrite));
if (c2pread != -1)
POSIX_CALL(close(c2pread));
if (errread != -1)
POSIX_CALL(close(errread));
POSIX_CALL(close(errpipe_read));
/* When duping fds, if there arises a situation where one of the fds is
either 0, 1 or 2, it is possible that it is overwritten (#12607). */
if (c2pwrite == 0)
POSIX_CALL(c2pwrite = dup(c2pwrite));
if (errwrite == 0 || errwrite == 1)
POSIX_CALL(errwrite = dup(errwrite));
/* Dup fds for child.
dup2() removes the CLOEXEC flag but we must do it ourselves if dup2()
would be a no-op (issue #10806). */
if (p2cread == 0) {
if (_Py_set_inheritable(p2cread, 1, NULL) < 0)
goto error;
}
else if (p2cread != -1)
POSIX_CALL(dup2(p2cread, 0)); /* stdin */
if (c2pwrite == 1) {
if (_Py_set_inheritable(c2pwrite, 1, NULL) < 0)
goto error;
}
else if (c2pwrite != -1)
POSIX_CALL(dup2(c2pwrite, 1)); /* stdout */
if (errwrite == 2) {
if (_Py_set_inheritable(errwrite, 1, NULL) < 0)
goto error;
}
else if (errwrite != -1)
POSIX_CALL(dup2(errwrite, 2)); /* stderr */
/* Close pipe fds. Make sure we don't close the same fd more than */
/* once, or standard fds. */
if (p2cread > 2)
POSIX_CALL(close(p2cread));
if (c2pwrite > 2 && c2pwrite != p2cread)
POSIX_CALL(close(c2pwrite));
if (errwrite != c2pwrite && errwrite != p2cread && errwrite > 2)
POSIX_CALL(close(errwrite));
if (cwd)
POSIX_CALL(chdir(cwd));
if (restore_signals)
_Py_RestoreSignals();
#ifdef HAVE_SETSID
if (call_setsid)
POSIX_CALL(setsid());
#endif
reached_preexec = 1;
if (preexec_fn != Py_None && preexec_fn_args_tuple) {
/* This is where the user has asked us to deadlock their program. */
result = PyObject_Call(preexec_fn, preexec_fn_args_tuple, NULL);
if (result == NULL) {
/* Stringifying the exception or traceback would involve
* memory allocation and thus potential for deadlock.
* We've already faced potential deadlock by calling back
* into Python in the first place, so it probably doesn't
* matter but we avoid it to minimize the possibility. */
err_msg = "Exception occurred in preexec_fn.";
errno = 0; /* We don't want to report an OSError. */
goto error;
}
/* Py_DECREF(result); - We're about to exec so why bother? */
}
/* close FDs after executing preexec_fn, which might open FDs */
if (close_fds) {
/* TODO HP-UX could use pstat_getproc() if anyone cares about it. */
_close_open_fds(3, py_fds_to_keep);
}
/* This loop matches the Lib/os.py _execvpe()'s PATH search when */
/* given the executable_list generated by Lib/subprocess.py. */
saved_errno = 0;
for (i = 0; exec_array[i] != NULL; ++i) {
const char *executable = exec_array[i];
if (envp) {
execve(executable, argv, envp);
} else {
execv(executable, argv);
}
if (errno != ENOENT && errno != ENOTDIR && saved_errno == 0) {
saved_errno = errno;
}
}
/* Report the first exec error, not the last. */
if (saved_errno)
errno = saved_errno;
error:
saved_errno = errno;
/* Report the posix error to our parent process. */
/* We ignore all write() return values as the total size of our writes is
less than PIPEBUF and we cannot do anything about an error anyways.
Use _Py_write_noraise() to retry write() if it is interrupted by a
signal (fails with EINTR). */
if (saved_errno) {
char *cur;
_Py_write_noraise(errpipe_write, "OSError:", 8);
cur = hex_errno + sizeof(hex_errno);
while (saved_errno != 0 && cur > hex_errno) {
*--cur = Py_hexdigits[saved_errno % 16];
saved_errno /= 16;
}
_Py_write_noraise(errpipe_write, cur, hex_errno + sizeof(hex_errno) - cur);
_Py_write_noraise(errpipe_write, ":", 1);
if (!reached_preexec) {
/* Indicate to the parent that the error happened before exec(). */
_Py_write_noraise(errpipe_write, "noexec", 6);
}
/* We can't call strerror(saved_errno). It is not async signal safe.
* The parent process will look the error message up. */
} else {
_Py_write_noraise(errpipe_write, "SubprocessError:0:", 18);
_Py_write_noraise(errpipe_write, err_msg, strlen(err_msg));
}
}
