gh-111856: Fix os.fstat on windows with FAT32 and exFAT filesystem (GH-112038)

aisk · web-flow · commit 29af7369dbbb · 2023-11-13T16:10:06.000Z
diff --git a/Misc/NEWS.d/next/Windows/2023-11-13-22-35-27.gh-issue-111856.vEtA5z.rst b/Misc/NEWS.d/next/Windows/2023-11-13-22-35-27.gh-issue-111856.vEtA5z.rst
@@ -0,0 +1,2 @@
+Fixes :func:`~os.fstat` on file systems that do not support file ID
+requests. This includes FAT32 and exFAT.
diff --git a/Python/fileutils.c b/Python/fileutils.c
@@ -1239,6 +1239,7 @@ _Py_fstat_noraise(int fd, struct _Py_stat_struct *status)
     BY_HANDLE_FILE_INFORMATION info;
     FILE_BASIC_INFO basicInfo;
     FILE_ID_INFO idInfo;
+    FILE_ID_INFO *pIdInfo = &idInfo;
     HANDLE h;
     int type;
 
@@ -1271,15 +1272,19 @@ _Py_fstat_noraise(int fd, struct _Py_stat_struct *status)
     }
 
     if (!GetFileInformationByHandle(h, &info) ||
-        !GetFileInformationByHandleEx(h, FileBasicInfo, &basicInfo, sizeof(basicInfo)) ||
-        !GetFileInformationByHandleEx(h, FileIdInfo, &idInfo, sizeof(idInfo))) {
+        !GetFileInformationByHandleEx(h, FileBasicInfo, &basicInfo, sizeof(basicInfo))) {
         /* The Win32 error is already set, but we also set errno for
            callers who expect it */
         errno = winerror_to_errno(GetLastError());
         return -1;
     }
 
-    _Py_attribute_data_to_stat(&info, 0, &basicInfo, &idInfo, status);
+    if (!GetFileInformationByHandleEx(h, FileIdInfo, &idInfo, sizeof(idInfo))) {
+        /* Failed to get FileIdInfo, so do not pass it along */
+        pIdInfo = NULL;
+    }
+
+    _Py_attribute_data_to_stat(&info, 0, &basicInfo, pIdInfo, status);
     return 0;
 #else
     return fstat(fd, status);
