From 1c1294be716d96e804aadafc249fcbfa8367621d Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 31 Aug 2022 16:23:20 -0400 Subject: [PATCH] Prevent long-term memory leakage in autovacuum launcher. get_database_list() failed to restore the caller's memory context, instead leaving current context set to TopMemoryContext which is how CommitTransactionCommand() leaves it. The callers both think they are using short-lived contexts, for the express purpose of not having to worry about cleaning up individual allocations. The net effect therefore is that supposedly short-lived allocations could accumulate indefinitely in the launcher's TopMemoryContext. Although this has been broken for a long time, it seems we didn't have any obvious memory leak here until v15's rearrangement of the stats logic. I (tgl) am not entirely convinced that there's no other leak at all, though, and we're surely at risk of adding one in future back-patched fixes. So back-patch to all supported branches, even though this may be only a latent bug in pre-v15. Reid Thompson Discussion: https://postgr.es/m/972a4e12b68b0f96db514777a150ceef7dcd2e0f.camel@crunchydata.com --- src/backend/postmaster/autovacuum.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index b3b1afba86..9dc6bf9477 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -1941,6 +1941,9 @@ get_database_list(void) CommitTransactionCommand(); + /* Be sure to restore caller's memory context */ + MemoryContextSwitchTo(resultcxt); + return dblist; }