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Fix heap-use-after-free on Http2Stream::destroy() #6346

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masaori335 merged 1 commit into from
Jan 27, 2020
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Fix heap-use-after-free on Http2Stream::destroy() #6346

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4 changes: 3 additions & 1 deletion proxy/http2/Http2Stream.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -757,6 +757,8 @@ Http2Stream::destroy()

// Safe to initiate SSN_CLOSE if this is the last stream
if (_proxy_ssn) {
cid = _proxy_ssn->connection_id();

Http2ClientSession *h2_proxy_ssn = static_cast<Http2ClientSession *>(_proxy_ssn);
SCOPED_MUTEX_LOCK(lock, h2_proxy_ssn->connection_state.mutex, this_ethread());
// Make sure the stream is removed from the stream list and priority tree
Expand All @@ -766,7 +768,7 @@ Http2Stream::destroy()
// Update session's stream counts, so it accurately goes into keep-alive state
h2_proxy_ssn->connection_state.release_stream(this);

cid = _proxy_ssn->connection_id();
// Do not access `_proxy_ssn` in below. It might be freed by `release_stream`.
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@maskit maskit Jan 27, 2020

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Looks familiar. Don't we have a similar comment somewhere? Or did we remove it and now putting it back? We may want something we can avoid the heap-use-after-free.

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@masaori335 masaori335 Jan 27, 2020

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This one? I agree with we need something.

trafficserver/proxy/http2/Http2ConnectionState.cc

Lines 1378 to 1382 in 48bcbe6

ua_session->destroy();
// Can't do this because we just destroyed right here ^,
// or we can use a local variable to do it.
// ua_session = nullptr;

}

// Clean up the write VIO in case of inactivity timeout
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