[3.12] gh-107913: Fix possible losses of OSError error codes (GH-107930) (#108523)

gh-107913: Fix possible losses of OSError error codes (GH-107930)

Functions like PyErr_SetFromErrno() and SetFromWindowsErr() should be
called immediately after using the C API which sets errno or the Windows
error code.
(cherry picked from commit 2b15536fa9)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Misc/NEWS.d/next/Library/2023-08-14-11-18-13.gh-issue-107913.4ooY6i.rst

@@ -0,0 +1,3 @@
+Fix possible losses of ``errno`` and ``winerror`` values in :exc:`OSError`
+exceptions if they were cleared or modified by the cleanup code before
+creating the exception object.

Modules/_cursesmodule.c

@@ -3071,8 +3071,8 @@ _curses_getwin(PyObject *module, PyObject *file)
     }
     datalen = PyBytes_GET_SIZE(data);
     if (fwrite(PyBytes_AS_STRING(data), 1, datalen, fp) != datalen) {
-        Py_DECREF(data);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_DECREF(data);
         goto error;
     }
     Py_DECREF(data);

Modules/_io/fileio.c

@@ -394,6 +394,11 @@ _io_FileIO___init___impl(fileio *self, PyObject *nameobj, const char *mode,
 
             if (async_err)
                 goto error;
+
+            if (self->fd < 0) {
+                PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, nameobj);
+                goto error;
+            }
         }
         else {
             PyObject *fdobj;
@@ -425,12 +430,7 @@ _io_FileIO___init___impl(fileio *self, PyObject *nameobj, const char *mode,
                 goto error;
             }
         }
-
         fd_is_own = 1;
-        if (self->fd < 0) {
-            PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, nameobj);
-            goto error;
-        }
 
 #ifndef MS_WINDOWS
         if (_Py_set_inheritable(self->fd, 0, atomic_flag_works) < 0)
@@ -1058,8 +1058,8 @@ _io_FileIO_truncate_impl(fileio *self, PyTypeObject *cls, PyObject *posobj)
     Py_END_ALLOW_THREADS
 
     if (ret != 0) {
-        Py_DECREF(posobj);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_DECREF(posobj);
         return NULL;
     }
 

Modules/_io/winconsoleio.c

@@ -378,8 +378,8 @@ _io__WindowsConsoleIO___init___impl(winconsoleio *self, PyObject *nameobj,
         else
             self->fd = _Py_open_osfhandle_noraise(handle, _O_RDONLY | _O_BINARY);
         if (self->fd < 0) {
-            CloseHandle(handle);
             PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, nameobj);
+            CloseHandle(handle);
             goto error;
         }
     }

Modules/_localemodule.c

@@ -737,8 +737,8 @@ _locale_bindtextdomain_impl(PyObject *module, const char *domain,
     }
     current_dirname = bindtextdomain(domain, dirname);
     if (current_dirname == NULL) {
-        Py_XDECREF(dirname_bytes);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_XDECREF(dirname_bytes);
         return NULL;
     }
     result = PyUnicode_DecodeLocale(current_dirname, NULL);

Modules/_multiprocessing/semaphore.c

@@ -516,12 +516,12 @@ _multiprocessing_SemLock_impl(PyTypeObject *type, int kind, int value,
     return result;
 
   failure:
-    if (handle != SEM_FAILED)
-        SEM_CLOSE(handle);
-    PyMem_Free(name_copy);
     if (!PyErr_Occurred()) {
         _PyMp_SetError(NULL, MP_STANDARD_ERROR);
     }
+    if (handle != SEM_FAILED)
+        SEM_CLOSE(handle);
+    PyMem_Free(name_copy);
     return NULL;
 }
 
@@ -556,8 +556,9 @@ _multiprocessing_SemLock__rebuild_impl(PyTypeObject *type, SEM_HANDLE handle,
     if (name != NULL) {
         handle = sem_open(name, 0);
         if (handle == SEM_FAILED) {
+            PyErr_SetFromErrno(PyExc_OSError);
             PyMem_Free(name_copy);
-            return PyErr_SetFromErrno(PyExc_OSError);
+            return NULL;
         }
     }
 #endif

Modules/_ssl.c

@@ -3889,8 +3889,8 @@ _ssl__SSLContext_load_cert_chain_impl(PySSLContext *self, PyObject *certfile,
             /* the password callback has already set the error information */
         }
         else if (errno != 0) {
-            ERR_clear_error();
             PyErr_SetFromErrno(PyExc_OSError);
+            ERR_clear_error();
         }
         else {
             _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
@@ -3910,8 +3910,8 @@ _ssl__SSLContext_load_cert_chain_impl(PySSLContext *self, PyObject *certfile,
             /* the password callback has already set the error information */
         }
         else if (errno != 0) {
-            ERR_clear_error();
             PyErr_SetFromErrno(PyExc_OSError);
+            ERR_clear_error();
         }
         else {
             _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
@@ -4140,8 +4140,8 @@ _ssl__SSLContext_load_verify_locations_impl(PySSLContext *self,
         PySSL_END_ALLOW_THREADS
         if (r != 1) {
             if (errno != 0) {
-                ERR_clear_error();
                 PyErr_SetFromErrno(PyExc_OSError);
+                ERR_clear_error();
             }
             else {
                 _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
@@ -4188,8 +4188,8 @@ _ssl__SSLContext_load_dh_params(PySSLContext *self, PyObject *filepath)
     PySSL_END_ALLOW_THREADS
     if (dh == NULL) {
         if (errno != 0) {
-            ERR_clear_error();
             PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, filepath);
+            ERR_clear_error();
         }
         else {
             _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);

Modules/faulthandler.c

@@ -414,11 +414,10 @@ faulthandler_allocate_stack(void)
 
     int err = sigaltstack(&stack, &old_stack);
     if (err) {
+        PyErr_SetFromErrno(PyExc_OSError);
         /* Release the stack to retry sigaltstack() next time */
         PyMem_Free(stack.ss_sp);
         stack.ss_sp = NULL;
-
-        PyErr_SetFromErrno(PyExc_OSError);
         return -1;
     }
     return 0;

Modules/fcntlmodule.c

@@ -211,11 +211,12 @@ fcntl_ioctl_impl(PyObject *module, int fd, unsigned int code,
             if (mutate_arg && (len <= IOCTL_BUFSZ)) {
                 memcpy(str, buf, len);
             }
-            PyBuffer_Release(&pstr); /* No further access to str below this point */
             if (ret < 0) {
                 PyErr_SetFromErrno(PyExc_OSError);
+                PyBuffer_Release(&pstr);
                 return NULL;
             }
+            PyBuffer_Release(&pstr);
             if (mutate_arg) {
                 return PyLong_FromLong(ret);
             }
@@ -240,8 +241,8 @@ fcntl_ioctl_impl(PyObject *module, int fd, unsigned int code,
             ret = ioctl(fd, code, buf);
             Py_END_ALLOW_THREADS
             if (ret < 0) {
-                PyBuffer_Release(&pstr);
                 PyErr_SetFromErrno(PyExc_OSError);
+                PyBuffer_Release(&pstr);
                 return NULL;
             }
             PyBuffer_Release(&pstr);

Modules/getpath.c

@@ -341,11 +341,12 @@ getpath_readlines(PyObject *Py_UNUSED(self), PyObject *args)
         return NULL;
     }
     FILE *fp = _Py_wfopen(path, L"rb");
-    PyMem_Free((void *)path);
     if (!fp) {
         PyErr_SetFromErrno(PyExc_OSError);
+        PyMem_Free((void *)path);
         return NULL;
     }
+    PyMem_Free((void *)path);
 
     r = PyList_New(0);
     if (!r) {

Modules/mmapmodule.c

@@ -1356,6 +1356,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
     m_obj->data = mmap(NULL, map_size, prot, flags, fd, offset);
     Py_END_ALLOW_THREADS
 
+    int saved_errno = errno;
     if (devzero != -1) {
         close(devzero);
     }
@@ -1363,6 +1364,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
     if (m_obj->data == (char *)-1) {
         m_obj->data = NULL;
         Py_DECREF(m_obj);
+        errno = saved_errno;
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }

Modules/overlapped.c

@@ -367,8 +367,9 @@ _overlapped_RegisterWaitWithQueue_impl(PyObject *module, HANDLE Object,
             &NewWaitObject, Object, PostToQueueCallback, pdata, Milliseconds,
             WT_EXECUTEINWAITTHREAD | WT_EXECUTEONLYONCE))
     {
+        SetFromWindowsErr(0);
         PyMem_RawFree(pdata);
-        return SetFromWindowsErr(0);
+        return NULL;
     }
 
     return Py_BuildValue(F_HANDLE, NewWaitObject);

Modules/posixmodule.c

@@ -3877,9 +3877,10 @@ posix_getcwd(int use_bytes)
         return NULL;
     }
     if (!len) {
+        PyErr_SetFromWindowsErr(0);
         if (wbuf2 != wbuf)
             PyMem_RawFree(wbuf2);
-        return PyErr_SetFromWindowsErr(0);
+        return NULL;
     }
 
     PyObject *resobj = PyUnicode_FromWideChar(wbuf2, len);
@@ -3927,8 +3928,9 @@ posix_getcwd(int use_bytes)
         return PyErr_NoMemory();
     }
     if (cwd == NULL) {
+        posix_error();
         PyMem_RawFree(buf);
-        return posix_error();
+        return NULL;
     }
 
     PyObject *obj;
@@ -4140,8 +4142,8 @@ _listdir_windows_no_opendir(path_t *path, PyObject *list)
         int error = GetLastError();
         if (error == ERROR_FILE_NOT_FOUND)
             goto exit;
-        Py_DECREF(list);
+        path_error(path);
-        list = path_error(path);
+        Py_CLEAR(list);
         goto exit;
     }
     do {
@@ -4154,12 +4156,12 @@ _listdir_windows_no_opendir(path_t *path, PyObject *list)
                 Py_SETREF(v, PyUnicode_EncodeFSDefault(v));
             }
             if (v == NULL) {
-                Py_SETREF(list, NULL);
+                Py_CLEAR(list);
                 break;
             }
             if (PyList_Append(list, v) != 0) {
                 Py_DECREF(v);
-                Py_SETREF(list, NULL);
+                Py_CLEAR(list);
                 break;
             }
             Py_DECREF(v);
@@ -4170,8 +4172,8 @@ _listdir_windows_no_opendir(path_t *path, PyObject *list)
         /* FindNextFile sets error to ERROR_NO_MORE_FILES if
            it got to the end of the directory. */
         if (!result && GetLastError() != ERROR_NO_MORE_FILES) {
-            Py_DECREF(list);
+            path_error(path);
-            list = path_error(path);
+            Py_CLEAR(list);
             goto exit;
         }
     } while (result == TRUE);
@@ -4180,8 +4182,8 @@ exit:
     if (hFindFile != INVALID_HANDLE_VALUE) {
         if (FindClose(hFindFile) == FALSE) {
             if (list != NULL) {
-                Py_DECREF(list);
+                path_error(path);
-                list = path_error(path);
+                Py_CLEAR(list);
             }
         }
     }
@@ -4243,7 +4245,8 @@ _posix_listdir(path_t *path, PyObject *list)
     }
 
     if (dirp == NULL) {
-        list = path_error(path);
+        path_error(path);
+        list = NULL;
 #ifdef HAVE_FDOPENDIR
         if (fd != -1) {
             Py_BEGIN_ALLOW_THREADS
@@ -4265,8 +4268,8 @@ _posix_listdir(path_t *path, PyObject *list)
             if (errno == 0) {
                 break;
             } else {
-                Py_DECREF(list);
+                path_error(path);
-                list = path_error(path);
+                Py_CLEAR(list);
                 goto exit;
             }
         }
@@ -6609,8 +6612,9 @@ os_execv_impl(PyObject *module, path_t *path, PyObject *argv)
 
     /* If we get here it's definitely an error */
 
+    posix_error();
     free_string_array(argvlist, argc);
-    return posix_error();
+    return NULL;
 }
 
 
@@ -6914,11 +6918,12 @@ parse_file_actions(PyObject *file_actions,
                 }
                 errno = posix_spawn_file_actions_addopen(file_actionsp,
                         fd, PyBytes_AS_STRING(path), oflag, (mode_t)mode);
-                Py_DECREF(path);
                 if (errno) {
                     posix_error();
+                    Py_DECREF(path);
                     goto fail;
                 }
+                Py_DECREF(path);
                 break;
             }
             case POSIX_SPAWN_CLOSE: {
@@ -7315,12 +7320,15 @@ os_spawnv_impl(PyObject *module, int mode, path_t *path, PyObject *argv)
     _Py_END_SUPPRESS_IPH
     Py_END_ALLOW_THREADS
 
+    int saved_errno = errno;
     free_string_array(argvlist, argc);
 
-    if (spawnval == -1)
+    if (spawnval == -1) {
-        return posix_error();
+        errno = saved_errno;
-    else
+        posix_error();
-        return Py_BuildValue(_Py_PARSE_INTPTR, spawnval);
+        return NULL;
+    }
+    return Py_BuildValue(_Py_PARSE_INTPTR, spawnval);
 }
 
 /*[clinic input]
@@ -7638,6 +7646,7 @@ os_fork1_impl(PyObject *module)
     }
     PyOS_BeforeFork();
     pid = fork1();
+    int saved_errno = errno;
     if (pid == 0) {
         /* child: this clobbers and resets the import lock. */
         PyOS_AfterFork_Child();
@@ -7646,8 +7655,10 @@ os_fork1_impl(PyObject *module)
         /* parent: release the import lock. */
         PyOS_AfterFork_Parent();
     }
-    if (pid == -1)
+    if (pid == -1) {
+        errno = saved_errno;
         return posix_error();
+    }
     return PyLong_FromPid(pid);
 }
 #endif /* HAVE_FORK1 */
@@ -7683,6 +7694,7 @@ os_fork_impl(PyObject *module)
     }
     PyOS_BeforeFork();
     pid = fork();
+    int saved_errno = errno;
     if (pid == 0) {
         /* child: this clobbers and resets the import lock. */
         PyOS_AfterFork_Child();
@@ -7691,8 +7703,10 @@ os_fork_impl(PyObject *module)
         /* parent: release the import lock. */
         PyOS_AfterFork_Parent();
     }
-    if (pid == -1)
+    if (pid == -1) {
+        errno = saved_errno;
         return posix_error();
+    }
     return PyLong_FromPid(pid);
 }
 #endif /* HAVE_FORK */
@@ -8229,13 +8243,17 @@ os_openpty_impl(PyObject *module)
 
     /* change permission of slave */
     if (grantpt(master_fd) < 0) {
+        int saved_errno = errno;
         PyOS_setsig(SIGCHLD, sig_saved);
+        errno = saved_errno;
         goto posix_error;
     }
 
     /* unlock slave */
     if (unlockpt(master_fd) < 0) {
+        int saved_errno = errno;
         PyOS_setsig(SIGCHLD, sig_saved);
+        errno = saved_errno;
         goto posix_error;
     }
 
@@ -8599,8 +8617,9 @@ os_getgroups_impl(PyObject *module)
 
     n = getgroups(n, grouplist);
     if (n == -1) {
+        posix_error();
         PyMem_Free(grouplist);
-        return posix_error();
+        return NULL;
     }
 
     PyObject *result = PyList_New(n);
@@ -9163,8 +9182,9 @@ os_setgroups(PyObject *module, PyObject *groups)
     }
 
     if (setgroups(len, grouplist) < 0) {
+        posix_error();
         PyMem_Free(grouplist);
-        return posix_error();
+        return NULL;
     }
     PyMem_Free(grouplist);
     Py_RETURN_NONE;
@@ -10611,10 +10631,13 @@ os_readv_impl(PyObject *module, int fd, PyObject *buffers)
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
+    int saved_errno = errno;
     iov_cleanup(iov, buf, cnt);
     if (n < 0) {
-        if (!async_err)
+        if (!async_err) {
+            errno = saved_errno;
             posix_error();
+        }
         return -1;
     }
 
@@ -10663,8 +10686,11 @@ os_pread_impl(PyObject *module, int fd, Py_ssize_t length, Py_off_t offset)
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
     if (n < 0) {
+        if (!async_err) {
+            posix_error();
+        }
         Py_DECREF(buffer);
-        return (!async_err) ? posix_error() : NULL;
+        return NULL;
     }
     if (n != length)
         _PyBytes_Resize(&buffer, n);
@@ -10761,9 +10787,11 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
 #endif
 
+    int saved_errno = errno;
     iov_cleanup(iov, buf, cnt);
     if (n < 0) {
         if (!async_err) {
+            errno = saved_errno;
             posix_error();
         }
         return -1;
@@ -10932,24 +10960,26 @@ os_sendfile_impl(PyObject *module, int out_fd, int in_fd, PyObject *offobj,
     } while (ret < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
     _Py_END_SUPPRESS_IPH
 
+    int saved_errno = errno;
     if (sf.headers != NULL)
         iov_cleanup(sf.headers, hbuf, sf.hdr_cnt);
     if (sf.trailers != NULL)
         iov_cleanup(sf.trailers, tbuf, sf.trl_cnt);
 
     if (ret < 0) {
-        if ((errno == EAGAIN) || (errno == EBUSY)) {
+        if ((saved_errno == EAGAIN) || (saved_errno == EBUSY)) {
             if (sbytes != 0) {
                 // some data has been sent
                 goto done;
             }
-            else {
+            // no data has been sent; upper application is supposed
-                // no data has been sent; upper application is supposed
+            // to retry on EAGAIN or EBUSY
-                // to retry on EAGAIN or EBUSY
-                return posix_error();
-            }
         }
-        return (!async_err) ? posix_error() : NULL;
+        if (!async_err) {
+            errno = saved_errno;
+            posix_error();
+        }
+        return NULL;
     }
     goto done;
 
@@ -11266,10 +11296,10 @@ os_writev_impl(PyObject *module, int fd, PyObject *buffers)
         Py_END_ALLOW_THREADS
     } while (result < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
-    iov_cleanup(iov, buf, cnt);
     if (result < 0 && !async_err)
         posix_error();
 
+    iov_cleanup(iov, buf, cnt);
     return result;
 }
 #endif /* HAVE_WRITEV */
@@ -11404,13 +11434,13 @@ os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
 #endif
 
-    iov_cleanup(iov, buf, cnt);
     if (result < 0) {
         if (!async_err) {
             posix_error();
         }
-        return -1;
+        result = -1;
     }
+    iov_cleanup(iov, buf, cnt);
 
     return result;
 }
@@ -11972,12 +12002,13 @@ win32_putenv(PyObject *name, PyObject *value)
        Prefer _wputenv() to be compatible with C libraries using CRT
        variables and CRT functions using these variables (ex: getenv()). */
     int err = _wputenv(env);
-    PyMem_Free(env);
 
     if (err) {
         posix_error();
+        PyMem_Free(env);
         return NULL;
     }
+    PyMem_Free(env);
 
     Py_RETURN_NONE;
 }
@@ -13819,10 +13850,12 @@ os_getxattr_impl(PyObject *module, path_t *path, path_t *attribute,
         Py_END_ALLOW_THREADS;
 
         if (result < 0) {
-            Py_DECREF(buffer);
+            if (errno == ERANGE) {
-            if (errno == ERANGE)
+                Py_DECREF(buffer);
                 continue;
+            }
             path_error(path);
+            Py_DECREF(buffer);
             return NULL;
         }
 
@@ -14589,14 +14622,19 @@ DirEntry_fetch_stat(PyObject *module, DirEntry *self, int follow_symlinks)
         }
         Py_END_ALLOW_THREADS
     }
+
+    int saved_errno = errno;
 #if defined(MS_WINDOWS)
     PyMem_Free(path);
 #else
     Py_DECREF(ub);
 #endif
 
-    if (result != 0)
+    if (result != 0) {
-        return path_object_error(self->path);
+        errno = saved_errno;
+        path_object_error(self->path);
+        return NULL;
+    }
 
     return _pystat_fromstructstat(module, &st);
 }
@@ -14788,10 +14826,14 @@ os_DirEntry_inode_impl(DirEntry *self)
         wchar_t *path = PyUnicode_AsWideCharString(unicode, NULL);
         Py_DECREF(unicode);
         result = LSTAT(path, &stat);
+
+        int saved_errno = errno;
         PyMem_Free(path);
 
-        if (result != 0)
+        if (result != 0) {
+            errno = saved_errno;
             return path_object_error(self->path);
+        }
 
         self->win32_file_index = stat.st_ino;
         self->got_file_index = 1;
@@ -15355,12 +15397,12 @@ os_scandir_impl(PyObject *module, path_t *path)
     iterator->handle = FindFirstFileW(path_strW, &iterator->file_data);
     Py_END_ALLOW_THREADS
 
-    PyMem_Free(path_strW);
-
     if (iterator->handle == INVALID_HANDLE_VALUE) {
         path_error(&iterator->path);
+        PyMem_Free(path_strW);
         goto error;
     }
+    PyMem_Free(path_strW);
 #else /* POSIX */
     errno = 0;
 #ifdef HAVE_FDOPENDIR

Modules/selectmodule.c

@@ -1292,8 +1292,8 @@ newPyEpoll_Object(PyTypeObject *type, int sizehint, SOCKET fd)
         self->epfd = fd;
     }
     if (self->epfd < 0) {
-        Py_DECREF(self);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_DECREF(self);
         return NULL;
     }
 
@@ -1971,8 +1971,8 @@ newKqueue_Object(PyTypeObject *type, SOCKET fd)
         self->kqfd = fd;
     }
     if (self->kqfd < 0) {
-        Py_DECREF(self);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_DECREF(self);
         return NULL;
     }
 

Modules/socketmodule.c

@@ -5401,8 +5401,8 @@ sock_initobj_impl(PySocketSockObject *self, int family, int type, int proto,
             }
 
             if (!SetHandleInformation((HANDLE)fd, HANDLE_FLAG_INHERIT, 0)) {
-                closesocket(fd);
                 PyErr_SetFromWindowsErr(0);
+                closesocket(fd);
                 return -1;
             }
 
@@ -5616,8 +5616,9 @@ socket_gethostname(PyObject *self, PyObject *unused)
                            name,
                            &size))
     {
+        PyErr_SetFromWindowsErr(0);
         PyMem_Free(name);
-        return PyErr_SetFromWindowsErr(0);
+        return NULL;
     }
 
     result = PyUnicode_FromWideChar(name, size);
@@ -6215,8 +6216,8 @@ socket_dup(PyObject *self, PyObject *fdobj)
     }
 
     if (!SetHandleInformation((HANDLE)newfd, HANDLE_FLAG_INHERIT, 0)) {
-        closesocket(newfd);
         PyErr_SetFromWindowsErr(0);
+        closesocket(newfd);
         return NULL;
     }
 #else
@@ -6663,11 +6664,12 @@ socket_inet_ntop(PyObject *self, PyObject *args)
 
     /* inet_ntop guarantee NUL-termination of resulting string. */
     retval = inet_ntop(af, packed_ip.buf, ip, sizeof(ip));
-    PyBuffer_Release(&packed_ip);
     if (!retval) {
         PyErr_SetFromErrno(PyExc_OSError);
+        PyBuffer_Release(&packed_ip);
         return NULL;
     } else {
+        PyBuffer_Release(&packed_ip);
         return PyUnicode_FromString(retval);
     }
 }
@@ -7006,8 +7008,8 @@ socket_if_nameindex(PyObject *self, PyObject *arg)
 
     ni = if_nameindex();
     if (ni == NULL) {
-        Py_DECREF(list);
         PyErr_SetFromErrno(PyExc_OSError);
+        Py_DECREF(list);
         return NULL;
     }
 

Objects/unicodeobject.c

@@ -7060,7 +7060,7 @@ decode_code_page_errors(UINT code_page,
             if (err != ERROR_NO_UNICODE_TRANSLATION
                 && err != ERROR_INSUFFICIENT_BUFFER)
             {
-                PyErr_SetFromWindowsErr(0);
+                PyErr_SetFromWindowsErr(err);
                 goto error;
             }
             insize++;

Python/fileutils.c

@@ -1790,6 +1790,7 @@ _Py_fopen_obj(PyObject *path, const char *mode)
         Py_END_ALLOW_THREADS
     } while (f == NULL
              && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+    int saved_errno = errno;
     PyMem_Free(wpath);
 #else
     PyObject *bytes;
@@ -1812,13 +1813,14 @@ _Py_fopen_obj(PyObject *path, const char *mode)
         Py_END_ALLOW_THREADS
     } while (f == NULL
              && errno == EINTR && !(async_err = PyErr_CheckSignals()));
-
+    int saved_errno = errno;
     Py_DECREF(bytes);
 #endif
     if (async_err)
         return NULL;
 
     if (f == NULL) {
+        errno = saved_errno;
         PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, path);
         return NULL;
     }