Jesse Long created PDFBOX-2815:
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Summary: Race conditions in COSStream decoding
Key: PDFBOX-2815
URL: https://issues.apache.org/jira/browse/PDFBOX-2815
Project: PDFBox
Issue Type: Bug
Components: PDModel
Affects Versions: 2.0.0
Environment: Slow filter decoders
Reporter: Jesse Long
Priority: Minor
In COSStream.getDecodeResult(), we have this:
if (unFilteredStream == null)
{
doDecode();
}
if (unFilteredStream == null || decodeResult == null)
{
... throw exception.... (supposedly, decode failed)
}
The problem is that there is a race condition here. If thread 1 enters this
method, it sees that unFilteredStream is null, so starts decoding. Before
actually running the decode, it creates unFilteredStream, then starts decode.
Now, thread 2 enters, sees that unFilteredStream is not null (thread 1 already
created it), gets to the next if statement, sees that decodeResult is null
(thread 1 is not finished decode yet), and thinks that the decode failed.
I have solved this on my side by creating:
private void ensureDecoded()
{
synchronized (this)
{
if (unFilteredStream == null)
{
doDecode();
}
}
}
and then replace all 3 instances of this:
if (unFilteredStream == null)
{
doDecode();
}
with this:
ensureDecoded();
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