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Fix wrong variable offset sanity check.

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Commit c7aeb775 rewrote the HOT-chain offset sanity checks in three
places, but in heap_get_root_tuples it accidentally tested offnum -- the
outer loop variable, which is already bounded by the loop condition --
instead of nextoffnum, the offset actually passed to PageGetItemId.  The
pre-c7aeb775 check tested nextoffnum.

With the check ineffective, a stale t_ctid could make PageGetItemId read
past the end of the line pointer array (which is data corruption that we
expect to be able to catch here).

Author: Peter Geoghegan <pg@bowt.ie>
Reported-by: Konstantin Knizhnik <knizhnik@garret.ru>
Discussion: https://postgr.es/m/87c7d8a4-3a82-4334-bee6-e8c2ad3f3293@garret.ru
Backpatch-through: 15
This commit is contained in:
Peter Geoghegan
2026-07-16 18:55:35 -04:00
parent 048067c04c
commit 64542957b4
1 changed files with 2 additions and 2 deletions
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4
src/backend/access/heap/pruneheap.c
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@@ -2374,14 +2374,14 @@ heap_get_root_tuples(Page page, OffsetNumber *root_offsets)
for (;;)
{
/* Sanity check (pure paranoia) */
if (offnum < FirstOffsetNumber)
if (nextoffnum < FirstOffsetNumber)
break;
/*
* An offset past the end of page's line pointer array is possible
* when the array was truncated
*/
if (offnum > maxoff)
if (nextoffnum > maxoff)
break;
lp = PageGetItemId(page, nextoffnum);