Guard against null plan pointer in CachedPlanIsSimplyValid().

tglsfdc · tglsfdc · commit 9089287aa037 · 2023-07-20T14:23:46.000-04:00
If both the passed-in plan pointer and plansource->gplan are NULL, CachedPlanIsSimplyValid would think that the plan pointer is possibly-valid and try to dereference it. For the one extant call site in plpgsql, this situation doesn't normally happen which is why we've not noticed. However, it appears to be possible if the previous use of the cached plan failed, as per report from Justin Pryzby. Add an extra check to prevent crashing. Back-patch to v13 where this code was added. Discussion: https://postgr.es/m/ZLlV+STFz1l/WhAQ@telsasoft.com
diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
@@ -1440,7 +1440,9 @@ CachedPlanIsSimplyValid(CachedPlanSource *plansource, CachedPlan *plan,
 	 * that here we *do* check plansource->is_valid, so as to force plan
 	 * rebuild if that's become false.
 	 */
-	if (!plansource->is_valid || plan != plansource->gplan || !plan->is_valid)
+	if (!plansource->is_valid ||
+		plan == NULL || plan != plansource->gplan ||
+		!plan->is_valid)
 		return false;
 
 	Assert(plan->magic == CACHEDPLAN_MAGIC);
