From: Amit Kapila <akapila@postgresql.org>
Date: Wed, 13 Jan 2021 03:01:45 +0000 (+0530)
Subject: Fix memory leak in SnapBuildSerialize.
X-Git-Tag: REL9_6_21~27
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=f2b268ee0626286d15a1eaa78fe1704811d51cd4;p=postgresql.git

Fix memory leak in SnapBuildSerialize.

The memory for the snapshot was leaked while serializing it to disk during
logical decoding. This memory will be freed only once walsender stops
streaming the changes. This can lead to a huge memory increase when master
logs Standby Snapshot too frequently say when the user is trying to create
many replication slots.

Reported-by: funnyxj.fxj@alibaba-inc.com
Diagnosed-by: funnyxj.fxj@alibaba-inc.com
Author: Amit Kapila
Backpatch-through: 9.5
Discussion: https://postgr.es/m/033ab54c-6393-42ee-8ec9-2b399b5d8cde.funnyxj.fxj@alibaba-inc.com
---

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index cdc117763cb..bba558705d1 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1464,7 +1464,7 @@ static void
 SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 {
 	Size		needed_length;
-	SnapBuildOnDisk *ondisk;
+	SnapBuildOnDisk *ondisk = NULL;
 	char	   *ondisk_c;
 	int			fd;
 	char		tmppath[MAXPGPATH];
@@ -1656,6 +1656,9 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 out:
 	ReorderBufferSetRestartPoint(builder->reorder,
 								 builder->last_serialized_snapshot);
+	/* be tidy */
+	if (ondisk)
+		pfree(ondisk);
 }
 
 /*