Catch stack overflow when recursing in transformFromClauseItem().

Most parts of the parser can expect that the stack overflow check
in transformExprRecurse() will trigger before things get desperate.
However, transformFromClauseItem() can recurse directly to self
without having analyzed any expressions, so it's possible to drive
it to a stack-overrun crash.  Add a check to prevent that.

Per bug #17583 from Egor Chindyaskin.  Back-patch to all supported
branches.

Richard Guo

Discussion: https://postgr.es/m/17583-33be55b9f981f75c@postgresql.org

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 5a18107e799b44798d385467fa550a35edc8ce0f..b85fbebd00eca4c6c6578a9ee792590c5101be24 100644 (file)
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1050,6 +1050,9 @@ transformFromClauseItem(ParseState *pstate, Node *n,
                        ParseNamespaceItem **top_nsitem,
                        List **namespace)
 {
+   /* Guard against stack overflow due to overly deep subtree */
+   check_stack_depth();
+
    if (IsA(n, RangeVar))
    {
        /* Plain relation reference, or perhaps a CTE reference */