Fix use-after-release mistake in currtid() and currtid2() for views

michaelpq · michaelpq · commit a36f216209b8 · 2020-06-01T14:41:37.000+09:00
This issue has been present since the introduction of this code as of a3519a2 from 2002, and has been found by buildfarm member prion that uses RELCACHE_FORCE_RELEASE via the tests introduced recently in e786be5. Discussion: https://postgr.es/m/20200601022055.GB4121@paquier.xyz Backpatch-through: 9.5
diff --git a/src/backend/utils/adt/tid.c b/src/backend/utils/adt/tid.c
@@ -309,8 +309,13 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
 					rte = rt_fetch(var->varno, query->rtable);
 					if (rte)
 					{
+						Datum		result;
+
+						result = DirectFunctionCall2(currtid_byreloid,
+													 ObjectIdGetDatum(rte->relid),
+													 PointerGetDatum(tid));
 						heap_close(viewrel, AccessShareLock);
-						return DirectFunctionCall2(currtid_byreloid, ObjectIdGetDatum(rte->relid), PointerGetDatum(tid));
+						return result;
 					}
 				}
 			}

Original file line number	Diff line number	Diff line change
`@@ -309,8 +309,13 @@ currtid_for_view(Relation viewrel, ItemPointer tid)`
`309`	`309`	`rte = rt_fetch(var->varno, query->rtable);`
`310`	`310`	`if (rte)`
`311`	`311`	`{`
	`312`	`+ Datum result;`
	`313`	`+`
	`314`	`+ result = DirectFunctionCall2(currtid_byreloid,`
	`315`	`+ ObjectIdGetDatum(rte->relid),`
	`316`	`+ PointerGetDatum(tid));`
`312`	`317`	`heap_close(viewrel, AccessShareLock);`
`313`		`- return DirectFunctionCall2(currtid_byreloid, ObjectIdGetDatum(rte->relid), PointerGetDatum(tid));`
	`318`	`+ return result;`
`314`	`319`	`}`
`315`	`320`	`}`
`316`	`321`	`}`