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Offset to next TAR block must be positive #10012

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Merged
radarhere merged 1 commit into from
Sep 17, 2026
Merged

Offset to next TAR block must be positive #10012

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14 changes: 14 additions & 0 deletions Tests/test_file_tar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -65,3 +65,17 @@ def test_contextmanager() -> None:
with warnings.catch_warnings(action="error"):
with TarIO.TarIO(TEST_TAR_FILE, "hopper.jpg"):
pass


@pytest.mark.parametrize("size", (b"-1", b"0"))
def test_odd(tmp_path: Path, size: bytes) -> None:
with open(TEST_TAR_FILE, "rb") as f:
data = bytearray(f.read())

data[124:135] = size.rjust(11)

tmpfile = tmp_path / "temp.tar"
tmpfile.write_bytes(data)

with pytest.raises(ValueError, match="offset must be positive"):
TarIO.TarIO(str(tmpfile), "test")
6 changes: 5 additions & 1 deletion src/PIL/TarIO.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,11 @@ def __init__(self, tarfile: str, file: str) -> None:
if file == name:
break

self.fh.seek((size + 511) & (~511), io.SEEK_CUR)
offset = (size + 511) & ~511
if offset <= 0:
msg = "offset must be positive"
raise ValueError(msg)
self.fh.seek(offset, io.SEEK_CUR)

# Open region
super().__init__(self.fh, self.fh.tell(), size)