v1-0001-basebackup-add-missing-deflateEnd-calls-in-gzip-comp.patch

From 5d1edeceafd422072c17026dfd1f862a19feb792 Mon Sep 17 00:00:00 2001
From: Jianghua Yang <yjhjstz@gmail.com>
Date: Fri, 20 Mar 2026 09:57:17 -0700
Subject: [PATCH] basebackup: add missing deflateEnd() calls in gzip
 compression sink

The gzip basebackup sink called deflateInit2() in begin_archive but
never called deflateEnd(), leaking zlib's internal compression state
(~256KB per archive) until the memory context was destroyed. It also
lacked a dedicated cleanup callback, so on ERROR the zlib context
was not released at all.

Add deflateEnd() at the end of bbsink_gzip_end_archive() for the
normal path, and add a new bbsink_gzip_cleanup() function for the
error path.  This brings the gzip sink in line with the lz4 and zstd
sinks, which already properly free their compression contexts in both
end_archive and cleanup callbacks.

Author: Jianghua Yang <yjhjstz@gmail.com>
---
 src/backend/backup/basebackup_gzip.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/backend/backup/basebackup_gzip.c b/src/backend/backup/basebackup_gzip.c
index 1ba25015ab7..c264a833429 100644
--- a/src/backend/backup/basebackup_gzip.c
+++ b/src/backend/backup/basebackup_gzip.c
@@ -32,6 +32,9 @@ typedef struct bbsink_gzip
 
 	/* Number of bytes staged in output buffer. */
 	size_t		bytes_written;
+
+	/* Has the zstream been initialized with deflateInit2? */
+	bool		zstream_initialized;
 } bbsink_gzip;
 
 static void bbsink_gzip_begin_backup(bbsink *sink);
@@ -39,6 +42,7 @@ static void bbsink_gzip_begin_archive(bbsink *sink, const char *archive_name);
 static void bbsink_gzip_archive_contents(bbsink *sink, size_t len);
 static void bbsink_gzip_manifest_contents(bbsink *sink, size_t len);
 static void bbsink_gzip_end_archive(bbsink *sink);
+static void bbsink_gzip_cleanup(bbsink *sink);
 static void *gzip_palloc(void *opaque, unsigned items, unsigned size);
 static void gzip_pfree(void *opaque, void *address);
 
@@ -51,7 +55,7 @@ static const bbsink_ops bbsink_gzip_ops = {
 	.manifest_contents = bbsink_gzip_manifest_contents,
 	.end_manifest = bbsink_forward_end_manifest,
 	.end_backup = bbsink_forward_end_backup,
-	.cleanup = bbsink_forward_cleanup
+	.cleanup = bbsink_gzip_cleanup
 };
 #endif
 
@@ -141,6 +145,7 @@ bbsink_gzip_begin_archive(bbsink *sink, const char *archive_name)
 		ereport(ERROR,
 				errcode(ERRCODE_INTERNAL_ERROR),
 				errmsg("could not initialize compression library"));
+	mysink->zstream_initialized = true;
 
 	/*
 	 * Add ".gz" to the archive name. Note that the pg_basebackup -z produces
@@ -266,6 +271,10 @@ bbsink_gzip_end_archive(bbsink *sink)
 		mysink->bytes_written = 0;
 	}
 
+	/* Release the compression resources. */
+	deflateEnd(zs);
+	mysink->zstream_initialized = false;
+
 	/* Must also pass on the information that this archive has ended. */
 	bbsink_forward_end_archive(sink);
 }
@@ -301,4 +310,20 @@ gzip_pfree(void *opaque, void *address)
 	pfree(address);
 }
 
+/*
+ * In case the backup fails, make sure we free the compression context by
+ * calling deflateEnd() if needed to avoid a resource leak.
+ */
+static void
+bbsink_gzip_cleanup(bbsink *sink)
+{
+	bbsink_gzip *mysink = (bbsink_gzip *) sink;
+
+	if (mysink->zstream_initialized)
+	{
+		deflateEnd(&mysink->zstream);
+		mysink->zstream_initialized = false;
+	}
+}
+
 #endif
-- 
2.50.1 (Apple Git-155)