https://github.com/python/cpython/commit/cb67b44ca92f9930b3aa2aba8420c89d12a25303
commit: cb67b44ca92f9930b3aa2aba8420c89d12a25303
branch: main
author: Bert Peters <[email protected]>
committer: serhiy-storchaka <[email protected]>
date: 2025-03-05T00:06:07+02:00
summary:
gh-127371 Avoid unbounded growth SpooledTempfile.writelines (GH-127372)
files:
A Misc/NEWS.d/next/Security/2024-11-28-20-29-21.gh-issue-127371.PeEhUd.rst
M Lib/tempfile.py
M Lib/test/test_tempfile.py
diff --git a/Lib/tempfile.py b/Lib/tempfile.py
index 0eb9ddeb6ac377..cadb0bed3cce3b 100644
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -868,10 +868,14 @@ def write(self, s):
return rv
def writelines(self, iterable):
- file = self._file
- rv = file.writelines(iterable)
- self._check(file)
- return rv
+ if self._max_size == 0 or self._rolled:
+ return self._file.writelines(iterable)
+
+ it = iter(iterable)
+ for line in it:
+ self.write(line)
+ if self._rolled:
+ return self._file.writelines(it)
def detach(self):
return self._file.detach()
diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py
index 7adc021d298254..d46d3c0f040601 100644
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -1284,6 +1284,34 @@ def test_writelines(self):
buf = f.read()
self.assertEqual(buf, b'xyz')
+ def test_writelines_rollover(self):
+ # Verify writelines rolls over before exhausting the iterator
+ f = self.do_create(max_size=2)
+
+ def it():
+ yield b'xy'
+ self.assertFalse(f._rolled)
+ yield b'z'
+ self.assertTrue(f._rolled)
+
+ f.writelines(it())
+ pos = f.seek(0)
+ self.assertEqual(pos, 0)
+ buf = f.read()
+ self.assertEqual(buf, b'xyz')
+
+ def test_writelines_fast_path(self):
+ f = self.do_create(max_size=2)
+ f.write(b'abc')
+ self.assertTrue(f._rolled)
+
+ f.writelines([b'd', b'e', b'f'])
+ pos = f.seek(0)
+ self.assertEqual(pos, 0)
+ buf = f.read()
+ self.assertEqual(buf, b'abcdef')
+
+
def test_writelines_sequential(self):
# A SpooledTemporaryFile should hold exactly max_size bytes, and roll
# over afterward
diff --git
a/Misc/NEWS.d/next/Security/2024-11-28-20-29-21.gh-issue-127371.PeEhUd.rst
b/Misc/NEWS.d/next/Security/2024-11-28-20-29-21.gh-issue-127371.PeEhUd.rst
new file mode 100644
index 00000000000000..029c348918e0d1
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2024-11-28-20-29-21.gh-issue-127371.PeEhUd.rst
@@ -0,0 +1,3 @@
+Avoid unbounded buffering for
:meth:`!tempfile.SpooledTemporaryFile.writelines`.
+Previously, disk spillover was only checked after the lines iterator had been
+exhausted. This is now done after each line is written.
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