From a3c4a91f1e283cc4b79f0b0482d2c490a599d880 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 9 Oct 2024 17:07:53 -0400 Subject: [PATCH] Avoid crash in estimate_array_length with null root pointer. Commit 9391f7152 added a "PlannerInfo *root" parameter to estimate_array_length, but failed to consider the possibility that NULL would be passed for that, leading to a null pointer dereference. We could rectify the particular case shown in the bug report by fixing simplify_function/inline_function to pass through the root pointer. However, as long as eval_const_expressions is documented to accept NULL for root, similar hazards would remain. For now, let's just do the narrow fix of hardening estimate_array_length to not crash. Its behavior with NULL root will be the same as it was before 9391f7152, so this is not too awful. Per report from Fredrik Widlert (via Paul Ramsey). Back-patch to v17 where 9391f7152 came in. Discussion: https://postgr.es/m/518339E7-173E-45EC-A0FF-9A4A62AA4F40@cleverelephant.ca --- src/backend/optimizer/path/costsize.c | 3 +++ src/backend/utils/adt/selfuncs.c | 5 ++++- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index ee23ed7835..52ebdd90fc 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -4635,6 +4635,9 @@ cost_rescan(PlannerInfo *root, Path *path, * preferred since it allows caching of the results.) * The result includes both a one-time (startup) component, * and a per-evaluation component. + * + * Note: in some code paths root can be passed as NULL, resulting in + * slightly worse estimates. */ void cost_qual_eval(QualCost *cost, List *quals, PlannerInfo *root) diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 5f5d7959d8..f4b3e91baa 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -2131,6 +2131,9 @@ scalararraysel(PlannerInfo *root, * * Note: the result is integral, but we use "double" to avoid overflow * concerns. Most callers will use it in double-type expressions anyway. + * + * Note: in some code paths root can be passed as NULL, resulting in + * slightly worse estimates. */ double estimate_array_length(PlannerInfo *root, Node *arrayexpr) @@ -2154,7 +2157,7 @@ estimate_array_length(PlannerInfo *root, Node *arrayexpr) { return list_length(((ArrayExpr *) arrayexpr)->elements); } - else if (arrayexpr) + else if (arrayexpr && root) { /* See if we can find any statistics about it */ VariableStatData vardata; -- 2.11.4.GIT