From 4186ab1a803003e68d721fbb0095fa62cf671c4a Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Mon, 17 Aug 2020 21:06:08 +0000
Subject: [PATCH] Drop bogus IPv6 messages
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Drop bogus IPv6 messages

RH-Author: Jon Maloy <jmaloy@redhat.com>
Message-id: <20200817220608.1142611-2-jmaloy@redhat.com>
Patchwork-id: 98161
O-Subject: [RHEL-AV-8.3.0 qemu-kvm PATCH 1/1] Drop bogus IPv6 messages
Bugzilla: 1838092 1867075 1870421
RH-Acked-by: Danilo de Paula <ddepaula@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>

From: Ralf Haferkamp <rhafer@suse.com>

Drop IPv6 message shorter than what's mentioned in the payload
length header (+ the size of the IPv6 header). They're invalid an could
lead to data leakage in icmp6_send_echoreply().

(cherry picked from libslirp commit c7ede54cbd2e2b25385325600958ba0124e31cc0)
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 slirp/ip6_input.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/slirp/ip6_input.c b/slirp/ip6_input.c
index ac2e3ea882..deb3d6e086 100644
--- a/slirp/ip6_input.c
+++ b/slirp/ip6_input.c
@@ -49,6 +49,13 @@ void ip6_input(struct mbuf *m)
         goto bad;
     }
 
+    // Check if the message size is big enough to hold what's
+    // set in the payload length header. If not this is an invalid
+    // packet
+    if (m->m_len < ntohs(ip6->ip_pl) + sizeof(struct ip6)) {
+        goto bad;
+    }
+
     /* check ip_ttl for a correct ICMP reply */
     if (ip6->ip_hl == 0) {
         icmp6_send_error(m, ICMP6_TIMXCEED, ICMP6_TIMXCEED_INTRANS);
-- 
2.27.0