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ORCA: Fix use-after-free in CXformSplitWindowFunc #1853

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ORCA: Fix use-after-free in CXformSplitWindowFunc #1853

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13 changes: 13 additions & 0 deletions src/backend/gporca/libgpopt/src/xforms/CXformSplitWindowFunc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -375,13 +375,26 @@ CXformSplitWindowFunc::Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexprLocalSelect =
GPOS_NEW(mp) CExpression(mp, pSelectCopy, pexprLocal, pexprScalarCmp);

// the global SequenceProject below takes ownership of one reference each to
// pds, pdrgpos and pdrgpwf, just like the local SequenceProject above. Only
// a single AddRef() was issued for each of them, so add the matching
// references here; otherwise the reference count underflows, these objects
// are freed while still in use, and the dangling memory later crashes the
// DXL-to-PlStmt translation (use-after-free)
pds->AddRef();
pdrgpos->AddRef();
pdrgpwf->AddRef();

CExpression *pexprGlobal = GPOS_NEW(mp)
CExpression(mp,
GPOS_NEW(mp) CLogicalSequenceProject(
mp, COperator::ESPType::EsptypeGlobalTwoStep, pds,
pdrgpos, pdrgpwf),
pexprLocalSelect, pexprProjectListGlobal);

pexpr->Pop()->AddRef();
pexprScalarCmp->AddRef();

CExpression *pexprGlobalSelect =
GPOS_NEW(mp) CExpression(mp, pexpr->Pop(), pexprGlobal, pexprScalarCmp);

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