avahi: apply fix for CVE-2021-3468

This patch isn't yet upstream but it has been submitted and other distros
are shipping it.

(From OE-Core rev: ea33a4a2df4600a55b268e9d57e7396c30f3d123)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-connectivity/avahi/avahi_0.8.bb

@@ -24,6 +24,7 @@ SRC_URI = "https://github.com/lathiat/avahi/releases/download/v${PV}/avahi-${PV}
            file://99avahi-autoipd \
            file://initscript.patch \
            file://0001-Fix-opening-etc-resolv.conf-error.patch \
+           file://handle-hup.patch \
            "
 
 UPSTREAM_CHECK_URI = "https://github.com/lathiat/avahi/releases/"

meta/recipes-connectivity/avahi/files/handle-hup.patch

@@ -0,0 +1,41 @@
+CVE: CVE-2021-3468
+Upstream-Status: Submitted [https://github.com/lathiat/avahi/pull/330]
+Signed-off-by: Ross Burton <ross.burton@arm.com>
+
+From 447affe29991ee99c6b9732fc5f2c1048a611d3b Mon Sep 17 00:00:00 2001
+From: Riccardo Schirone <sirmy15@gmail.com>
+Date: Fri, 26 Mar 2021 11:50:24 +0100
+Subject: [PATCH] Avoid infinite-loop in avahi-daemon by handling HUP event in
+ client_work
+
+If a client fills the input buffer, client_work() disables the
+AVAHI_WATCH_IN event, thus preventing the function from executing the
+`read` syscall the next times it is called. However, if the client then
+terminates the connection, the socket file descriptor receives a HUP
+event, which is not handled, thus the kernel keeps marking the HUP event
+as occurring. While iterating over the file descriptors that triggered
+an event, the client file descriptor will keep having the HUP event and
+the client_work() function is always called with AVAHI_WATCH_HUP but
+without nothing being done, thus entering an infinite loop.
+
+See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=984938
+---
+ avahi-daemon/simple-protocol.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/avahi-daemon/simple-protocol.c b/avahi-daemon/simple-protocol.c
+index 3e0ebb11..6c0274d6 100644
+--- a/avahi-daemon/simple-protocol.c
++++ b/avahi-daemon/simple-protocol.c
+@@ -424,6 +424,11 @@ static void client_work(AvahiWatch *watch, AVAHI_GCC_UNUSED int fd, AvahiWatchEv
+         }
+     }
+ 
++    if (events & AVAHI_WATCH_HUP) {
++        client_free(c);
++        return;
++    }
++
+     c->server->poll_api->watch_update(
+         watch,
+         (c->outbuf_length > 0 ? AVAHI_WATCH_OUT : 0) |