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

michaelpq · michaelpq · commit ce1c5b9ae87b · 2020-06-01T14:41:18.000+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
@@ -338,8 +338,13 @@ 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));
 						table_close(viewrel, AccessShareLock);
-						return DirectFunctionCall2(currtid_byreloid, ObjectIdGetDatum(rte->relid), PointerGetDatum(tid));
+						return result;
 					}
 				}
 			}

Original file line number	Diff line number	Diff line change
`@@ -338,8 +338,13 @@ currtid_for_view(Relation viewrel, ItemPointer tid)`
`338`	`338`	`rte = rt_fetch(var->varno, query->rtable);`
`339`	`339`	`if (rte)`
`340`	`340`	`{`
	`341`	`+ Datum result;`
	`342`	`+`
	`343`	`+ result = DirectFunctionCall2(currtid_byreloid,`
	`344`	`+ ObjectIdGetDatum(rte->relid),`
	`345`	`+ PointerGetDatum(tid));`
`341`	`346`	`table_close(viewrel, AccessShareLock);`
`342`		`- return DirectFunctionCall2(currtid_byreloid, ObjectIdGetDatum(rte->relid), PointerGetDatum(tid));`
	`347`	`+ return result;`
`343`	`348`	`}`
`344`	`349`	`}`
`345`	`350`	`}`