From 4352ca234e979ad1c7158981addf899b119cd448 Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Sun, 20 Mar 2022 07:51:11 -0700 Subject: [PATCH] bpo-42369: Fix thread safety of zipfile._SharedFile.tell (GH-26974) The `_SharedFile` tracks its own virtual position into the file as `self._pos` and updates it after reading or seeking. `tell()` should return this position instead of calling into the underlying file object, since if multiple `_SharedFile` instances are being used concurrently on the same file, another one may have moved the real file position. Additionally, calling into the underlying `tell` may expose thread safety issues in the underlying file object because it was called without taking the lock. (cherry picked from commit e730ae7effe4f13b24f1b5fb1fca005709c86acb) Co-authored-by: Kevin Mehall --- Lib/zipfile.py | 4 +++- .../next/Library/2022-03-19-19-56-04.bpo-42369.Ok828t.rst | 1 + 2 files changed, 4 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Library/2022-03-19-19-56-04.bpo-42369.Ok828t.rst diff --git a/Lib/zipfile.py b/Lib/zipfile.py index 67cfdfb6aafc..34d2fa4b8642 100644 --- a/Lib/zipfile.py +++ b/Lib/zipfile.py @@ -721,7 +721,9 @@ class _SharedFile: self._lock = lock self._writing = writing self.seekable = file.seekable - self.tell = file.tell + + def tell(self): + return self._pos def seek(self, offset, whence=0): with self._lock: diff --git a/Misc/NEWS.d/next/Library/2022-03-19-19-56-04.bpo-42369.Ok828t.rst b/Misc/NEWS.d/next/Library/2022-03-19-19-56-04.bpo-42369.Ok828t.rst new file mode 100644 index 000000000000..86dc3a0b81b9 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-03-19-19-56-04.bpo-42369.Ok828t.rst @@ -0,0 +1 @@ +Fix thread safety of :meth:`zipfile._SharedFile.tell` to avoid a "zipfile.BadZipFile: Bad CRC-32 for file" exception when reading a :class:`ZipFile` from multiple threads. -- 2.47.3