From 66c074b707318005d50f14910678ba451877a7a6 Mon Sep 17 00:00:00 2001
From: Petr Mensik <pemensik@redhat.com>
Date: Wed, 19 Jun 2019 12:28:08 +0200
Subject: [PATCH] Fix CVE-2019-6471
5244. [security] Fixed a race condition in dns_dispatch_getnext()
that could cause an assertion failure if a
significant number of incoming packets were
rejected. (CVE-2019-6471) [GL #942]
---
lib/dns/dispatch.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/lib/dns/dispatch.c b/lib/dns/dispatch.c
index 321459ebcb..ae5c9c0fc7 100644
--- a/lib/dns/dispatch.c
+++ b/lib/dns/dispatch.c
@@ -3419,13 +3419,14 @@ dns_dispatch_getnext(dns_dispentry_t *resp, dns_dispatchevent_t **sockevent) {
disp = resp->disp;
REQUIRE(VALID_DISPATCH(disp));
- REQUIRE(resp->item_out == ISC_TRUE);
- resp->item_out = ISC_FALSE;
-
ev = *sockevent;
*sockevent = NULL;
LOCK(&disp->lock);
+
+ REQUIRE(resp->item_out == ISC_TRUE);
+ resp->item_out = ISC_FALSE;
+
if (ev->buffer.base != NULL)
free_buffer(disp, ev->buffer.base, ev->buffer.length);
free_devent(disp, ev);
@@ -3570,6 +3571,9 @@ dns_dispatch_removeresponse(dns_dispentry_t **resp,
isc_task_send(disp->task[0], &disp->ctlevent);
}
+/*
+ * disp must be locked.
+ */
static void
do_cancel(dns_dispatch_t *disp) {
dns_dispatchevent_t *ev;
--
2.20.1