From 2d6a778f7335cd21f8e7bc4d12f2162441bc2e69 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Fri, 21 Mar 2025 11:21:40 +0100
Subject: [PATCH] [3.12] gh-131492, gh-131461: handle exceptions in GzipFile
 constructor while owning resources (GH-131462) (#131519)

(cherry picked from commit ce79274e9f093bd06d2285c9af48dbcbc92173de)

Co-authored-by: Thomas Grainger <tagrain@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Lib/gzip.py                                   | 100 ++++++++++--------
 Lib/test/test_tarfile.py                      |  11 +-
 ...-03-20-08-32-49.gh-issue-131492.saC2cA.rst |   1 +
 3 files changed, 63 insertions(+), 49 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-03-20-08-32-49.gh-issue-131492.saC2cA.rst

diff --git a/Lib/gzip.py b/Lib/gzip.py
index 01a791e5824..ecfe3a9cd7e 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -195,51 +195,58 @@ def __init__(self, filename=None, mode=None,
             raise ValueError("Invalid mode: {!r}".format(mode))
         if mode and 'b' not in mode:
             mode += 'b'
-        if fileobj is None:
-            fileobj = self.myfileobj = builtins.open(filename, mode or 'rb')
-        if filename is None:
-            filename = getattr(fileobj, 'name', '')
-            if not isinstance(filename, (str, bytes)):
-                filename = ''
-        else:
-            filename = os.fspath(filename)
-        origmode = mode
-        if mode is None:
-            mode = getattr(fileobj, 'mode', 'rb')
+
+        try:
+            if fileobj is None:
+                fileobj = self.myfileobj = builtins.open(filename, mode or 'rb')
+            if filename is None:
+                filename = getattr(fileobj, 'name', '')
+                if not isinstance(filename, (str, bytes)):
+                    filename = ''
+            else:
+                filename = os.fspath(filename)
+            origmode = mode
+            if mode is None:
+                mode = getattr(fileobj, 'mode', 'rb')
 
 
-        if mode.startswith('r'):
-            self.mode = READ
-            raw = _GzipReader(fileobj)
-            self._buffer = io.BufferedReader(raw)
-            self.name = filename
+            if mode.startswith('r'):
+                self.mode = READ
+                raw = _GzipReader(fileobj)
+                self._buffer = io.BufferedReader(raw)
+                self.name = filename
 
-        elif mode.startswith(('w', 'a', 'x')):
-            if origmode is None:
-                import warnings
-                warnings.warn(
-                    "GzipFile was opened for writing, but this will "
-                    "change in future Python releases.  "
-                    "Specify the mode argument for opening it for writing.",
-                    FutureWarning, 2)
-            self.mode = WRITE
-            self._init_write(filename)
-            self.compress = zlib.compressobj(compresslevel,
-                                             zlib.DEFLATED,
-                                             -zlib.MAX_WBITS,
-                                             zlib.DEF_MEM_LEVEL,
-                                             0)
-            self._write_mtime = mtime
-            self._buffer_size = _WRITE_BUFFER_SIZE
-            self._buffer = io.BufferedWriter(_WriteBufferStream(self),
-                                             buffer_size=self._buffer_size)
-        else:
-            raise ValueError("Invalid mode: {!r}".format(mode))
+            elif mode.startswith(('w', 'a', 'x')):
+                if origmode is None:
+                    import warnings
+                    warnings.warn(
+                        "GzipFile was opened for writing, but this will "
+                        "change in future Python releases.  "
+                        "Specify the mode argument for opening it for writing.",
+                        FutureWarning, 2)
+                self.mode = WRITE
+                self._init_write(filename)
+                self.compress = zlib.compressobj(compresslevel,
+                                                 zlib.DEFLATED,
+                                                 -zlib.MAX_WBITS,
+                                                 zlib.DEF_MEM_LEVEL,
+                                                 0)
+                self._write_mtime = mtime
+                self._buffer_size = _WRITE_BUFFER_SIZE
+                self._buffer = io.BufferedWriter(_WriteBufferStream(self),
+                                                 buffer_size=self._buffer_size)
+            else:
+                raise ValueError("Invalid mode: {!r}".format(mode))
 
-        self.fileobj = fileobj
+            self.fileobj = fileobj
 
-        if self.mode == WRITE:
-            self._write_gzip_header(compresslevel)
+            if self.mode == WRITE:
+                self._write_gzip_header(compresslevel)
+        except:
+            # Avoid a ResourceWarning if the write fails,
+            # eg read-only file or KeyboardInterrupt
+            self._close()
+            raise
 
     @property
     def mtime(self):
@@ -368,11 +375,14 @@ def close(self):
             elif self.mode == READ:
                 self._buffer.close()
         finally:
-            self.fileobj = None
-            myfileobj = self.myfileobj
-            if myfileobj:
-                self.myfileobj = None
-                myfileobj.close()
+            self._close()
+
+    def _close(self):
+        self.fileobj = None
+        myfileobj = self.myfileobj
+        if myfileobj is not None:
+            self.myfileobj = None
+            myfileobj.close()
 
     def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
         self._check_not_closed()
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index e28d0311826..ae55bebbc80 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -1615,10 +1615,13 @@ def write(self, data):
                         raise exctype
 
             f = BadFile()
-            with self.assertRaises(exctype):
-                tar = tarfile.open(tmpname, self.mode, fileobj=f,
-                                   format=tarfile.PAX_FORMAT,
-                                   pax_headers={'non': 'empty'})
+            with (
+                warnings_helper.check_no_resource_warning(self),
+                self.assertRaises(exctype),
+            ):
+                tarfile.open(tmpname, self.mode, fileobj=f,
+                             format=tarfile.PAX_FORMAT,
+                             pax_headers={'non': 'empty'})
             self.assertFalse(f.closed)
 
 
diff --git a/Misc/NEWS.d/next/Library/2025-03-20-08-32-49.gh-issue-131492.saC2cA.rst b/Misc/NEWS.d/next/Library/2025-03-20-08-32-49.gh-issue-131492.saC2cA.rst
new file mode 100644
index 00000000000..0f52dec7ce8
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-03-20-08-32-49.gh-issue-131492.saC2cA.rst
@@ -0,0 +1 @@
+Fix a resource leak when constructing a :class:`gzip.GzipFile` with a filename fails, for example when passing an invalid ``compresslevel``.