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- 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 3d3f7a9beaeba6908d6c4d74a1afddf246968cbe..56c84e1e629c749d296ebb858b684ff91a0ce138 100644 (file)
--- 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);