From ac20fa249f129b5c1eb65d378baf4f954dd03bc9 Mon Sep 17 00:00:00 2001
From: Eric van Gyzen <vangyzen@FreeBSD.org>
Date: Fri, 23 Jul 2021 08:49:55 -0500
Subject: [PATCH] aio_md_test: NUL-terminate result of readlink

readlink does not NUL-terminate the output buffer.  This led to spurious
failures to destroy the md device because the unit number was garbage.
NUL-terminate the output buffer.

Reported by:	ASLR
MFC after:	1 week
Sponsored by:	Dell EMC Isilon

(cherry picked from commit ea0e1b19f232331bffa75a0a64a6859c40f1cc4d)
---
 tests/sys/aio/aio_test.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/sys/aio/aio_test.c b/tests/sys/aio/aio_test.c
index af2e3823d1ff..0f929c510e9f 100644
--- a/tests/sys/aio/aio_test.c
+++ b/tests/sys/aio/aio_test.c
@@ -767,8 +767,9 @@ aio_md_cleanup(void)
 		    strerror(errno));
 		return;
 	}
-	n = readlink(MDUNIT_LINK, buf, sizeof(buf));
+	n = readlink(MDUNIT_LINK, buf, sizeof(buf) - 1);
 	if (n > 0) {
+		buf[n] = '\0';
 		if (sscanf(buf, "%d", &unit) == 1 && unit >= 0) {
 			bzero(&mdio, sizeof(mdio));
 			mdio.md_version = MDIOVERSION;