/* Authors: Gregory P. Smith & Jeffrey Yasskin */
#include "Python.h"
#if defined(HAVE_PIPE2) && !defined(_GNU_SOURCE)
# define _GNU_SOURCE
#endif
#include
#include
#ifdef HAVE_SYS_TYPES_H
#include
#endif
#if defined(HAVE_SYS_STAT_H) && defined(__FreeBSD__)
#include
#endif
#ifdef HAVE_SYS_SYSCALL_H
#include
#endif
#if defined(HAVE_SYS_RESOURCE_H)
#include
#endif
#ifdef HAVE_DIRENT_H
#include
#endif
#if defined(__ANDROID__) && __ANDROID_API__ < 21 && !defined(SYS_getdents64)
# include
# define SYS_getdents64 __NR_getdents64
#endif
#if defined(sun)
/* readdir64 is used to work around Solaris 9 bug 6395699. */
# define readdir readdir64
# define dirent dirent64
# if !defined(HAVE_DIRFD)
/* Some versions of Solaris lack dirfd(). */
# define dirfd(dirp) ((dirp)->dd_fd)
# define HAVE_DIRFD
# endif
#endif
#if defined(__FreeBSD__) || (defined(__APPLE__) && defined(__MACH__))
# define FD_DIR "/dev/fd"
#else
# define FD_DIR "/proc/self/fd"
#endif
#define POSIX_CALL(call) do { if ((call) == -1) goto error; } while (0)
/* If gc was disabled, call gc.enable(). Return 0 on success. */
static int
_enable_gc(int need_to_reenable_gc, PyObject *gc_module)
{
PyObject *result;
_Py_IDENTIFIER(enable);
PyObject *exctype, *val, *tb;
if (need_to_reenable_gc) {
PyErr_Fetch(&exctype, &val, &tb);
result = _PyObject_CallMethodId(gc_module, &PyId_enable, NULL);
if (exctype != NULL) {
PyErr_Restore(exctype, val, tb);
}
if (result == NULL) {
return 1;
}
Py_DECREF(result);
}
return 0;
}
/* Convert ASCII to a positive int, no libc call. no overflow. -1 on error. */
static int
_pos_int_from_ascii(const char *name)
{
int num = 0;
while (*name >= '0' && *name 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));
}
}
static PyObject *
subprocess_fork_exec(PyObject* self, PyObject *args)
{
PyObject *gc_module = NULL;
PyObject *executable_list, *py_fds_to_keep;
PyObject *env_list, *preexec_fn;
PyObject *process_args, *converted_args = NULL, *fast_args = NULL;
PyObject *preexec_fn_args_tuple = NULL;
int p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite;
int errpipe_read, errpipe_write, close_fds, restore_signals;
int call_setsid;
PyObject *cwd_obj, *cwd_obj2;
const char *cwd;
pid_t pid;
int need_to_reenable_gc = 0;
char *const *exec_array, *const *argv = NULL, *const *envp = NULL;
Py_ssize_t arg_num;
int need_after_fork = 0;
if (!PyArg_ParseTuple(
args, "OOpO!OOiiiiiiiiiiO:fork_exec",
&process_args, &executable_list,
&close_fds, &PyTuple_Type, &py_fds_to_keep,
&cwd_obj, &env_list,
&p2cread, &p2cwrite, &c2pread, &c2pwrite,
&errread, &errwrite, &errpipe_read, &errpipe_write,
&restore_signals, &call_setsid, &preexec_fn))
return NULL;
if (close_fds && errpipe_write < 3) { /* precondition */
PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3");
return NULL;
}
if (_sanity_check_python_fd_sequence(py_fds_to_keep)) {
PyErr_SetString(PyExc_ValueError, "bad value(s) in fds_to_keep");
return NULL;
}
/* We need to call gc.disable() when we'll be calling preexec_fn */
if (preexec_fn != Py_None) {
PyObject *result;
_Py_IDENTIFIER(isenabled);
_Py_IDENTIFIER(disable);
gc_module = PyImport_ImportModule("gc");
if (gc_module == NULL)
return NULL;
result = _PyObject_CallMethodId(gc_module, &PyId_isenabled, NULL);
if (result == NULL) {
Py_DECREF(gc_module);
return NULL;
}
need_to_reenable_gc = PyObject_IsTrue(result);
Py_DECREF(result);
if (need_to_reenable_gc == -1) {
Py_DECREF(gc_module);
return NULL;
}
result = _PyObject_CallMethodId(gc_module, &PyId_disable, NULL);
if (result == NULL) {
Py_DECREF(gc_module);
return NULL;
}
Py_DECREF(result);
}
exec_array = _PySequence_BytesToCharpArray(executable_list);
if (!exec_array)
goto cleanup;
/* Convert args and env into appropriate arguments for exec() */
/* These conversions are done in the parent process to avoid allocating
or freeing memory in the child process. */
if (process_args != Py_None) {
Py_ssize_t num_args;
/* Equivalent to: */
/* tuple(PyUnicode_FSConverter(arg) for arg in process_args) */
fast_args = PySequence_Fast(process_args, "argv must be a tuple");
if (fast_args == NULL)
goto cleanup;
num_args = PySequence_Fast_GET_SIZE(fast_args);
converted_args = PyTuple_New(num_args);
if (converted_args == NULL)
goto cleanup;
for (arg_num = 0; arg_num < num_args; ++arg_num) {
PyObject *borrowed_arg, *converted_arg;
if (PySequence_Fast_GET_SIZE(fast_args) != num_args) {
PyErr_SetString(PyExc_RuntimeError, "args changed during iteration");
goto cleanup;
}
PyObject *arg = PySequence_Fast_GetItemRef(fast_args, arg_num);
if (PyUnicode_FSConverter(arg, &converted_arg) == 0) {
Py_DECREF(arg);
goto cleanup;
}
Py_DECREF(arg);
PyTuple_SetItemRef(converted_args, arg_num, converted_arg);
Py_DECREF(converted_arg);
}
argv = _PySequence_BytesToCharpArray(converted_args);
Py_CLEAR(converted_args);
Py_CLEAR(fast_args);
if (!argv)
goto cleanup;
}
if (env_list != Py_None) {
envp = _PySequence_BytesToCharpArray(env_list);
if (!envp)
goto cleanup;
}
if (cwd_obj != Py_None) {
if (PyUnicode_FSConverter(cwd_obj, &cwd_obj2) == 0)
goto cleanup;
cwd = PyBytes_AsString(cwd_obj2);
} else {
cwd = NULL;
cwd_obj2 = NULL;
}
/* This must be the last thing done before fork() because we do not
* want to call PyOS_BeforeFork() if there is any chance of another
* error leading to the cleanup: code without calling fork(). */
if (preexec_fn != Py_None) {
preexec_fn_args_tuple = PyTuple_New(0);
if (!preexec_fn_args_tuple)
goto cleanup;
PyOS_BeforeFork();
need_after_fork = 1;
}
pid = fork();
if (pid == 0) {
/* Child process */
/*
* Code from here to _exit() must only use async-signal-safe functions,
* listed at `man 7 signal` or
* http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
*/
if (preexec_fn != Py_None) {
/* We'll be calling back into Python later so we need to do this.
* This call may not be async-signal-safe but neither is calling
* back into Python. The user asked us to use hope as a strategy
* to avoid deadlock... */
PyOS_AfterFork_Child();
}
child_exec(exec_array, argv, envp, cwd,
p2cread, p2cwrite, c2pread, c2pwrite,
errread, errwrite, errpipe_read, errpipe_write,
close_fds, restore_signals, call_setsid,
py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);
_exit(255);
return NULL; /* Dead code to avoid a potential compiler warning. */
}
Py_XDECREF(cwd_obj2);
if (pid == -1) {
/* Capture the errno exception before errno can be clobbered. */
PyErr_SetFromErrno(PyExc_OSError);
}
/* Parent process */
if (need_after_fork)
PyOS_AfterFork_Parent();
if (envp)
_Py_FreeCharPArray(envp);
if (argv)
_Py_FreeCharPArray(argv);
_Py_FreeCharPArray(exec_array);
/* Reenable gc in the parent process (or if fork failed). */
if (_enable_gc(need_to_reenable_gc, gc_module)) {
pid = -1;
}
Py_XDECREF(preexec_fn_args_tuple);
Py_XDECREF(gc_module);
if (pid == -1)
return NULL; /* fork() failed. Exception set earlier. */
return PyLong_FromPid(pid);
cleanup:
if (envp)
_Py_FreeCharPArray(envp);
if (argv)
_Py_FreeCharPArray(argv);
if (exec_array)
_Py_FreeCharPArray(exec_array);
Py_XDECREF(converted_args);
Py_XDECREF(fast_args);
Py_XDECREF(preexec_fn_args_tuple);
_enable_gc(need_to_reenable_gc, gc_module);
Py_XDECREF(gc_module);
return NULL;
}
PyDoc_STRVAR(subprocess_fork_exec_doc,
"fork_exec(args, executable_list, close_fds, cwd, env,\n\
p2cread, p2cwrite, c2pread, c2pwrite,\n\
errread, errwrite, errpipe_read, errpipe_write,\n\
restore_signals, call_setsid, preexec_fn)\n\
\n\
Forks a child process, closes parent file descriptors as appropriate in the\n\
child and dups the few that are needed before calling exec() in the child\n\
process.\n\
\n\
The preexec_fn, if supplied, will be called immediately before exec.\n\
WARNING: preexec_fn is NOT SAFE if your application uses threads.\n\
It may trigger infrequent, difficult to debug deadlocks.\n\
\n\
If an error occurs in the child process before the exec, it is\n\
serialized and written to the errpipe_write fd per subprocess.py.\n\
\n\
Returns: the child process's PID.\n\
\n\
Raises: Only on an error in the parent process.\n\
");
/* module level code ********************************************************/
PyDoc_STRVAR(module_doc,
"A POSIX helper for the subprocess module.");
static PyMethodDef module_methods[] = {
{"fork_exec", subprocess_fork_exec, METH_VARARGS, subprocess_fork_exec_doc},
{NULL, NULL} /* sentinel */
};
static struct PyModuleDef _posixsubprocessmodule = {
PyModuleDef_HEAD_INIT,
"_posixsubprocess",
module_doc,
-1, /* No memory is needed. */
module_methods,
};
PyMODINIT_FUNC
PyInit__posixsubprocess(void)
{
return PyModule_Create(&_posixsubprocessmodule);
}