| /* Authors: Gregory P. Smith & Jeffrey Yasskin */ |
| #include "Python.h" |
| #if defined(HAVE_PIPE2) && !defined(_GNU_SOURCE) |
| # define _GNU_SOURCE |
| #endif |
| #include <unistd.h> |
| #include <fcntl.h> |
| |
| |
| #define POSIX_CALL(call) if ((call) == -1) goto error |
| |
| |
| /* Maximum file descriptor, initialized on module load. */ |
| static long max_fd; |
| |
| |
| /* Given the gc module call gc.enable() and return 0 on success. */ |
| static int _enable_gc(PyObject *gc_module) |
| { |
| PyObject *result; |
| result = PyObject_CallMethod(gc_module, "enable", NULL); |
| if (result == NULL) |
| return 1; |
| Py_DECREF(result); |
| return 0; |
| } |
| |
| |
| /* |
| * 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, Py_ssize_t num_fds_to_keep, |
| PyObject *py_fds_to_keep, |
| PyObject *preexec_fn, |
| PyObject *preexec_fn_args_tuple) |
| { |
| int i, saved_errno, fd_num; |
| 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]; |
| |
| /* 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) { |
| int old = fcntl(p2cread, F_GETFD); |
| if (old != -1) |
| fcntl(p2cread, F_SETFD, old & ~FD_CLOEXEC); |
| } else if (p2cread != -1) { |
| POSIX_CALL(dup2(p2cread, 0)); /* stdin */ |
| } |
| if (c2pwrite == 1) { |
| int old = fcntl(c2pwrite, F_GETFD); |
| if (old != -1) |
| fcntl(c2pwrite, F_SETFD, old & ~FD_CLOEXEC); |
| } else if (c2pwrite != -1) { |
| POSIX_CALL(dup2(c2pwrite, 1)); /* stdout */ |
| } |
| if (errwrite == 2) { |
| int old = fcntl(errwrite, F_GETFD); |
| if (old != -1) |
| fcntl(errwrite, F_SETFD, old & ~FD_CLOEXEC); |
| } 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)); |
| } |
| |
| /* close() is intentionally not checked for errors here as we are closing */ |
| /* a large range of fds, some of which may be invalid. */ |
| if (close_fds) { |
| Py_ssize_t keep_seq_idx; |
| int start_fd = 3; |
| for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) { |
| PyObject* py_keep_fd = PySequence_Fast_GET_ITEM(py_fds_to_keep, |
| keep_seq_idx); |
| int keep_fd = PyLong_AsLong(py_keep_fd); |
| if (keep_fd < 0) { /* Negative number, overflow or not a Long. */ |
| err_msg = "bad value in fds_to_keep."; |
| errno = 0; /* We don't want to report an OSError. */ |
| goto error; |
| } |
| if (keep_fd < start_fd) |
| continue; |
| for (fd_num = start_fd; fd_num < keep_fd; ++fd_num) { |
| close(fd_num); |
| } |
| start_fd = keep_fd + 1; |
| } |
| if (start_fd <= max_fd) { |
| for (fd_num = start_fd; fd_num < max_fd; ++fd_num) { |
| close(fd_num); |
| } |
| } |
| } |
| |
| if (cwd) |
| POSIX_CALL(chdir(cwd)); |
| |
| if (restore_signals) |
| _Py_RestoreSignals(); |
| |
| #ifdef HAVE_SETSID |
| if (call_setsid) |
| POSIX_CALL(setsid()); |
| #endif |
| |
| 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? */ |
| } |
| |
| /* 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. */ |
| if (saved_errno) { |
| char *cur; |
| write(errpipe_write, "OSError:", 8); |
| cur = hex_errno + sizeof(hex_errno); |
| while (saved_errno != 0 && cur > hex_errno) { |
| *--cur = "0123456789ABCDEF"[saved_errno % 16]; |
| saved_errno /= 16; |
| } |
| write(errpipe_write, cur, hex_errno + sizeof(hex_errno) - cur); |
| write(errpipe_write, ":", 1); |
| /* We can't call strerror(saved_errno). It is not async signal safe. |
| * The parent process will look the error message up. */ |
| } else { |
| write(errpipe_write, "RuntimeError:0:", 15); |
| write(errpipe_write, err_msg, strlen(err_msg)); |
| } |
| } |
| |
| |
| static PyObject * |
| subprocess_fork_exec(PyObject* self, PyObject *args) |
| { |
| PyObject *gc_module = NULL; |
| PyObject *executable_list, *py_close_fds, *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, num_fds_to_keep; |
| |
| if (!PyArg_ParseTuple( |
| args, "OOOOOOiiiiiiiiiiO:fork_exec", |
| &process_args, &executable_list, &py_close_fds, &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; |
| |
| close_fds = PyObject_IsTrue(py_close_fds); |
| if (close_fds && errpipe_write < 3) { /* precondition */ |
| PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3"); |
| return NULL; |
| } |
| num_fds_to_keep = PySequence_Length(py_fds_to_keep); |
| if (num_fds_to_keep < 0) { |
| PyErr_SetString(PyExc_ValueError, "bad 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; |
| gc_module = PyImport_ImportModule("gc"); |
| if (gc_module == NULL) |
| return NULL; |
| result = PyObject_CallMethod(gc_module, "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_CallMethod(gc_module, "disable", NULL); |
| if (result == NULL) { |
| Py_DECREF(gc_module); |
| return NULL; |
| } |
| Py_DECREF(result); |
| } |
| |
| exec_array = _PySequence_BytesToCharpArray(executable_list); |
| if (!exec_array) |
| return NULL; |
| |
| /* 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"); |
| 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; |
| borrowed_arg = PySequence_Fast_GET_ITEM(fast_args, arg_num); |
| if (PyUnicode_FSConverter(borrowed_arg, &converted_arg) == 0) |
| goto cleanup; |
| PyTuple_SET_ITEM(converted_args, arg_num, 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 (preexec_fn != Py_None) { |
| preexec_fn_args_tuple = PyTuple_New(0); |
| if (!preexec_fn_args_tuple) |
| goto cleanup; |
| _PyImport_AcquireLock(); |
| } |
| |
| 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; |
| } |
| |
| 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_exec(exec_array, argv, envp, cwd, |
| p2cread, p2cwrite, c2pread, c2pwrite, |
| errread, errwrite, errpipe_read, errpipe_write, |
| close_fds, restore_signals, call_setsid, |
| num_fds_to_keep, 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); |
| } |
| if (preexec_fn != Py_None && |
| _PyImport_ReleaseLock() < 0 && !PyErr_Occurred()) { |
| PyErr_SetString(PyExc_RuntimeError, |
| "not holding the import lock"); |
| } |
| |
| /* Parent process */ |
| 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 (need_to_reenable_gc && _enable_gc(gc_module)) { |
| Py_XDECREF(gc_module); |
| return NULL; |
| } |
| 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); |
| _Py_FreeCharPArray(exec_array); |
| Py_XDECREF(converted_args); |
| Py_XDECREF(fast_args); |
| Py_XDECREF(preexec_fn_args_tuple); |
| |
| /* Reenable gc if it was disabled. */ |
| if (need_to_reenable_gc) |
| _enable_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\ |
| "); |
| |
| PyDoc_STRVAR(subprocess_cloexec_pipe_doc, |
| "cloexec_pipe() -> (read_end, write_end)\n\n\ |
| Create a pipe whose ends have the cloexec flag set."); |
| |
| static PyObject * |
| subprocess_cloexec_pipe(PyObject *self, PyObject *noargs) |
| { |
| int fds[2]; |
| int res; |
| #ifdef HAVE_PIPE2 |
| Py_BEGIN_ALLOW_THREADS |
| res = pipe2(fds, O_CLOEXEC); |
| Py_END_ALLOW_THREADS |
| if (res != 0 && errno == ENOSYS) |
| { |
| if (PyErr_WarnEx( |
| PyExc_RuntimeWarning, |
| "pipe2 set errno ENOSYS; falling " |
| "back to non-atomic pipe+fcntl.", 1) != 0) { |
| return NULL; |
| } |
| { |
| #endif |
| /* We hold the GIL which offers some protection from other code calling |
| * fork() before the CLOEXEC flags have been set but we can't guarantee |
| * anything without pipe2(). */ |
| long oldflags; |
| |
| res = pipe(fds); |
| |
| if (res == 0) { |
| oldflags = fcntl(fds[0], F_GETFD, 0); |
| if (oldflags < 0) res = oldflags; |
| } |
| if (res == 0) |
| res = fcntl(fds[0], F_SETFD, oldflags | FD_CLOEXEC); |
| |
| if (res == 0) { |
| oldflags = fcntl(fds[1], F_GETFD, 0); |
| if (oldflags < 0) res = oldflags; |
| } |
| if (res == 0) |
| res = fcntl(fds[1], F_SETFD, oldflags | FD_CLOEXEC); |
| #ifdef HAVE_PIPE2 |
| } |
| } |
| #endif |
| if (res != 0) |
| return PyErr_SetFromErrno(PyExc_OSError); |
| return Py_BuildValue("(ii)", fds[0], fds[1]); |
| } |
| |
| /* 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}, |
| {"cloexec_pipe", subprocess_cloexec_pipe, METH_NOARGS, subprocess_cloexec_pipe_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) |
| { |
| #ifdef _SC_OPEN_MAX |
| max_fd = sysconf(_SC_OPEN_MAX); |
| if (max_fd == -1) |
| #endif |
| max_fd = 256; /* Matches Lib/subprocess.py */ |
| |
| return PyModule_Create(&_posixsubprocessmodule); |
| } |