From 543e6569a3f4730f3105379cc946cc6b54525179 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 24 Nov 2023 14:13:10 +0200 Subject: [PATCH 1/4] Turn tail recursion into iteration in CommitTransactionCommand() Usually the compiler will optimize away the tail recursion anyway, but if it doesn't, you can drive the function into stack overflow. For example: (n=1000000; printf "BEGIN;"; for ((i=1;i<=$n;i++)); do printf "SAVEPOINT s$i;"; done; printf "ERROR; COMMIT;") | psql >/dev/null Report by Egor Chindyaskin and Alexander Lakhin. Discussion: https://www.postgresql.org/message-id/1672760457.940462079%40f306.i.mail.ru --- src/backend/access/transam/xact.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 536edb3792..e16b73a9f1 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -3033,12 +3033,15 @@ RestoreTransactionCharacteristics(const SavedTransactionCharacteristics *s) void CommitTransactionCommand(void) { - TransactionState s = CurrentTransactionState; + TransactionState s; SavedTransactionCharacteristics savetc; +recurse: + s = CurrentTransactionState; /* Must save in case we need to restore below */ SaveTransactionCharacteristics(&savetc); + s = CurrentTransactionState; switch (s->blockState) { /* @@ -3226,8 +3229,7 @@ CommitTransactionCommand(void) */ case TBLOCK_SUBABORT_END: CleanupSubTransaction(); - CommitTransactionCommand(); - break; + goto recurse; /* * As above, but it's not dead yet, so abort first. @@ -3235,8 +3237,7 @@ CommitTransactionCommand(void) case TBLOCK_SUBABORT_PENDING: AbortSubTransaction(); CleanupSubTransaction(); - CommitTransactionCommand(); - break; + goto recurse; /* * The current subtransaction is the target of a ROLLBACK TO -- 2.39.2