Guard against null plan pointer in CachedPlanIsSimplyValid().

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/[email protected]

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index b481cac55662f51b024310a7e353a5b83e606fc8..73fb2011b4817c7001e73f38efff48228e934f52 100644 (file)
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -1436,7 +1436,9 @@ 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);