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