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bpo-42146: Unify cleanup in subprocess_fork_exec() (GH-22970) 

* bpo-42146: Unify cleanup in subprocess_fork_exec()

Also ignore errors from _enable_gc():
* They are always suppressed by the current code due to a bug.
* _enable_gc() is only used if `preexec_fn != None`, which is unsafe.
* We don't have a good way to handle errors in case we successfully
  created a child process.

Co-authored-by: Gregory P. Smith <greg@krypto.org>
This commit is contained in:
Alexey Izbyshev 2020-11-01 08:33:08 +03:00 committed by GitHub
parent 3bf0d02f28
commit d3b4e06807
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 18 additions and 35 deletions
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53
Modules/_posixsubprocess.c
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@ -87,8 +87,8 @@ get_posixsubprocess_state(PyObject *module)
#define _posixsubprocessstate_global get_posixsubprocess_state(PyState_FindModule(&_posixsubprocessmodule))
/* If gc was disabled, call gc.enable(). Return 0 on success. */
static int
/* If gc was disabled, call gc.enable(). Ignore errors. */
static void
_enable_gc(int need_to_reenable_gc, PyObject *gc_module)
{
PyObject *result;
@ -98,15 +98,17 @@ _enable_gc(int need_to_reenable_gc, PyObject *gc_module)
PyErr_Fetch(&exctype, &val, &tb);
result = PyObject_CallMethodNoArgs(
gc_module, _posixsubprocessstate_global->enable);
if (result == NULL) {
/* We might have created a child process at this point, we
* we have no good way to handle a failure to reenable GC
* and return information about the child process. */
PyErr_Print();
}
Py_XDECREF(result);
if (exctype != NULL) {
PyErr_Restore(exctype, val, tb);
}
if (result == NULL) {
return 1;
}
Py_DECREF(result);
}
return 0;
}
@ -774,7 +776,7 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
int child_umask;
PyObject *cwd_obj, *cwd_obj2 = NULL;
const char *cwd;
pid_t pid;
pid_t pid = -1;
int need_to_reenable_gc = 0;
char *const *exec_array, *const *argv = NULL, *const *envp = NULL;
Py_ssize_t arg_num, num_groups = 0;
@ -1010,8 +1012,6 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
sigset_t all_sigs;
sigfillset(&all_sigs);
if ((saved_errno = pthread_sigmask(SIG_BLOCK, &all_sigs, &old_sigs))) {
errno = saved_errno;
PyErr_SetFromErrno(PyExc_OSError);
goto cleanup;
}
old_sigmask = &old_sigs;
@ -1050,50 +1050,33 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
}
#endif
Py_XDECREF(cwd_obj2);
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;
}
PyMem_RawFree(groups);
Py_XDECREF(preexec_fn_args_tuple);
Py_XDECREF(gc_module);
if (pid == -1) {
cleanup:
if (saved_errno != 0) {
errno = saved_errno;
/* We can't call this above as PyOS_AfterFork_Parent() calls back
* into Python code which would see the unreturned error. */
PyErr_SetFromErrno(PyExc_OSError);
return NULL; /* fork() failed. */
}
return PyLong_FromPid(pid);
cleanup:
Py_XDECREF(preexec_fn_args_tuple);
PyMem_RawFree(groups);
Py_XDECREF(cwd_obj2);
if (envp)
_Py_FreeCharPArray(envp);
Py_XDECREF(converted_args);
Py_XDECREF(fast_args);
if (argv)
_Py_FreeCharPArray(argv);
if (exec_array)
_Py_FreeCharPArray(exec_array);
PyMem_RawFree(groups);
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;
return pid == -1 ? NULL : PyLong_FromPid(pid);
}