From: Andres Freund <andres@anarazel.de>
Date: Wed, 23 Mar 2022 20:05:25 +0000 (-0700)
Subject: Don't call fwrite() with len == 0 when writing out relcache init file.
X-Git-Tag: REL_14_3~66
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=89a94c24aadd8f40084339ea3d16e2e14fa9f629;p=thirdparty%2Fpostgresql.git

Don't call fwrite() with len == 0 when writing out relcache init file.

Noticed via -fsanitize=undefined.

Backpatch to all branches, for the same reasons as 46ab07ffda9.

Discussion: https://postgr.es/m/20220323173537.ll7klrglnp4gn2um@alap3.anarazel.de
Backpatch: 10-
---

diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index b54c9117669..dcf56d47900 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -6485,7 +6485,7 @@ write_item(const void *data, Size len, FILE *fp)
 {
 	if (fwrite(&len, 1, sizeof(len), fp) != sizeof(len))
 		elog(FATAL, "could not write init file");
-	if (fwrite(data, 1, len, fp) != len)
+	if (len > 0 && fwrite(data, 1, len, fp) != len)
 		elog(FATAL, "could not write init file");
 }