From: Peter Eisentraut <peter@eisentraut.org>
Date: Wed, 15 Jul 2026 08:58:13 +0000 (+0200)
Subject: Add assertion about ssize_t narrowing in AIO code
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=01f78a84bf5aca4c00fe1168381830aca6f1b873;p=thirdparty%2Fpostgresql.git

Add assertion about ssize_t narrowing in AIO code

The result from pg_preadv() or pg_pwritev(), which is of type ssize_t,
is assigned to PgAioHandle.result, which is of type int.  This should
be ok because the maximum result is limited by PG_IOV_MAX times
BLCKSZ.  Add an assertion and a code comment to explain and check
this.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://www.postgresql.org/message-id/flat/f9aab072-0078-49e4-ab93-3b08086a4406@eisentraut.org
---

diff --git a/src/backend/storage/aio/aio_io.c b/src/backend/storage/aio/aio_io.c
index 72b4c9feb3a..132868130e7 100644
--- a/src/backend/storage/aio/aio_io.c
+++ b/src/backend/storage/aio/aio_io.c
@@ -141,6 +141,11 @@ pgaio_io_perform_synchronously(PgAioHandle *ioh)
 			elog(ERROR, "trying to execute invalid IO operation");
 	}
 
+	/*
+	 * ssize_t to int conversion should be ok because result should be no more
+	 * than PG_IOV_MAX times BLCKSZ.
+	 */
+	Assert(result <= INT_MAX);
 	ioh->result = result < 0 ? -errno : result;
 
 	pgaio_io_process_completion(ioh, ioh->result);