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Fix dereference of dangling pointer in GiST index buffering build. #383

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Merged
reshke merged 1 commit into from
May 7, 2026
Merged

Fix dereference of dangling pointer in GiST index buffering build. #383

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17 changes: 13 additions & 4 deletions src/backend/access/gist/gistbuild.c
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Original file line number Diff line number Diff line change
Expand Up @@ -476,6 +476,19 @@ gistBuildCallback(Relation index,
itup = gistFormTuple(buildstate->giststate, index, values, isnull, true);
itup->t_tid = *tupleId;

/* Update tuple count and total size. */
buildstate->indtuples += 1;
buildstate->indtuplesSize += IndexTupleSize(itup);

/*
* XXX In buffering builds, the tempCxt is also reset down inside
* gistProcessEmptyingQueue(). This is not great because it risks
* confusion and possible use of dangling pointers (for example, itup
* might be already freed when control returns here). It's generally
* better that a memory context be "owned" by only one function. However,
* currently this isn't causing issues so it doesn't seem worth the amount
* of refactoring that would be needed to avoid it.
*/
if (buildstate->bufferingMode == GIST_BUFFERING_ACTIVE)
{
/* We have buffers, so use them. */
Expand All @@ -491,10 +504,6 @@ gistBuildCallback(Relation index,
buildstate->giststate);
}

/* Update tuple count and total size. */
buildstate->indtuples += 1;
buildstate->indtuplesSize += IndexTupleSize(itup);

MemoryContextSwitchTo(oldCtx);
MemoryContextReset(buildstate->giststate->tempCxt);

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