Skip to content

[3.15] gh-151981: Make tarfile._Stream.seek break at EOF (GH-151982) #151991

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
StanFromIreland merged 1 commit into from
Jun 23, 2026
+21 −1
Merged

[3.15] gh-151981: Make tarfile._Stream.seek break at EOF (GH-151982) #151991

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 3 additions & 1 deletion Lib/tarfile.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -520,7 +520,9 @@ def seek(self, pos=0):
if pos - self.pos >= 0:
blocks, remainder = divmod(pos - self.pos, self.bufsize)
for i in range(blocks):
self.read(self.bufsize)
data = self.read(self.bufsize)
if not data:
break
self.read(remainder)
else:
raise StreamError("seeking backwards is not allowed")
Expand Down
16 changes: 16 additions & 0 deletions Lib/test/test_tarfile.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4802,6 +4802,22 @@ def valueerror_filter(tarinfo, path):
with self.check_context(arc.open(errorlevel='boo!'), filtererror_filter):
self.expect_exception(TypeError) # errorlevel is not int

@support.subTests('format', [tarfile.GNU_FORMAT, tarfile.PAX_FORMAT])
def test_getmembers_big_size(self, format):
# gh-151981: A loop in seek() for streaming files tried to read the
# declared number of blocks even at EOF
tinfo = tarfile.TarInfo("huge-file")
tinfo.size = 1 << 64
bio = io.BytesIO()
# Write header without data
bio.write(tinfo.tobuf(format))

# Reset & try to get contents
bio.seek(0)
with tarfile.open(fileobj=bio, mode="r|") as tar:
with self.assertRaises(tarfile.ReadError):
tar.getmembers()


class OverwriteTests(archiver_tests.OverwriteTests, unittest.TestCase):
testdir = os.path.join(TEMPDIR, "testoverwrite")
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Security/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
In :mod:`tarfile`, seeking a stream now stops when end of the stream is
reached.
Loading