From: Ondřej Surý <ondrej@isc.org>
Date: Thu, 11 Jun 2020 11:01:26 +0000 (+0200)
Subject: Add missing acquire memory barrier in isc_nmhandle_unref
X-Git-Tag: v9.17.3~59^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1013c0930e11e8a24d66da3dbdea26f72d25cbc2;p=thirdparty%2Fbind9.git

Add missing acquire memory barrier in isc_nmhandle_unref

The ThreadSanitizer uses system synchronization primitives to check for
data race.  The netmgr handle->references was missing acquire memory
barrier before resetting and reusing the memory occupied by isc_nmhandle_t.
---

diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index 9e4b692f801..35469b6dff1 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -1156,6 +1156,8 @@ isc_nmhandle_unref(isc_nmhandle_t *handle) {
 	if (isc_refcount_decrement(&handle->references) > 1) {
 		return;
 	}
+	/* We need an acquire memory barrier here */
+	(void)isc_refcount_current(&handle->references);
 
 	sock = handle->sock;
 	handle->sock = NULL;