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Avoid treating nonrequired nbtree keys as required.

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Consistently prevent nbtree array advancement from treating a scankey as
required when operating in pstate.forcenonrequired mode.  Otherwise, we
risk a NULL pointer dereference.  This was possible in the path where
_bt_check_compare is called to recheck a tuple that advanced all of the
scan's arrays to matching values: its continuescan=false handling
expects _bt_advance_array_keys to have been called with a valid pstate,
but it'll always be NULL during sktrig_required=false calls (which is
how _bt_advance_array_keys must be called when pstate.forcenonrequired).

Oversight in commit 8a510275, which optimized nbtree search scan key
comparisons.

Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/CAHgHdKsn2W=gPBmj7p6MjQFvxB+zZDBkwTSg0o3f5Hh8rkRrsA@mail.gmail.com
Discussion: https://postgr.es/m/CAH2-WzmodSE+gpTd1CRGU9ez8ytyyDS+Kns2r9NzgUp1s56kpw@mail.gmail.com
This commit is contained in:
Peter Geoghegan 2025-05-02 17:50:58 -04:00
parent 1681a70df3
commit 0f08df4068
1 changed files with 1 additions and 3 deletions
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4
src/backend/access/nbtree/nbtutils.c
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@ -1826,7 +1826,7 @@ _bt_advance_array_keys(IndexScanDesc scan, BTReadPageState *pstate,
/* Recheck _bt_check_compare on behalf of caller */
if (_bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, false,
false, &continuescan,
!sktrig_required, &continuescan,
&nsktrig) &&
!so->scanBehind)
{
@ -2799,8 +2799,6 @@ _bt_check_compare(IndexScanDesc scan, ScanDirection dir,
{
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Assert(!forcenonrequired || advancenonrequired);
*continuescan = true; /* default assumption */
for (; *ikey < so->numberOfKeys; (*ikey)++)