UNDERTOW-2424: Prevent connection access-after-free allowed through ChunkedStreamSinkConduit #1648
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…hunkedStreamSinkConduit ChunkedStreamSinkConduit releases underlying connections for reuse via a conduit listener, however flush calls may still be passed through after writes are terminated and successfully flushed. This would cause requests to be clobbered when the connection had already been reused to send another request, breaking the threading model.
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Specifics of the scenario in #1495: (note that line numbers may be slightly off due to debug statements I added in testing, method names/paths should be equivalent) The exchange is completed here: However with roughly this stack trace: The problem is, once the exchange ended, another request has already been parsed, so a |
carterkozak
commented
Aug 14, 2024
| @@ -200,6 +200,9 @@ int doWrite(final ByteBuffer src) throws IOException { | |||
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| @Override | |||
| public void truncateWrites() throws IOException { | |||
| if (anyAreSet(state, FLAG_FINISHED)) { | |||
| return; | |||
| } | |||
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I think we have another subtle bug in this method. The invokeFinishListener() is called prior to the finally, so the connection may already be used by another thread by the time we call truncateWrites. I'll push an update shortly.
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On second thought, this shouldn't matter in practice because terminateWrites will close the underlying persistent connection, so we don't need to worry about reuse.
baranowb
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Aug 22, 2024
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Jira: https://issues.redhat.com/browse/UNDERTOW-2424
2.2.x PR: #1652
2.3.x PR: #1653
ChunkedStreamSinkConduit releases underlying connections for reuse via a conduit listener, however flush calls may still be passed through after writes are terminated and successfully flushed. This would cause requests to be clobbered when the connection had already been reused to send another request, breaking the threading model.
This resolves the issue from #1495
For posterity: My first attempt at a fix was #1645 which resolves the issue, but I think this PR is cleaner and more precise. As always, I'm happy to throw the code out if you prefer a different approach, the important piece is the analysis of the root cause of the failures, which I believe I understand at this point :-)