From 30feadb676a0792036a0f64309235c5767e2ee76 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Fri, 4 Jun 2021 16:32:55 +0400
Subject: [PATCH 4/7] upd6: check udp6_input buffer size
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Fixes: CVE-2021-3593
Fixes: https://gitlab.freedesktop.org/slirp/libslirp/-/issues/45

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
(cherry picked from commit de71c15de66ba9350bf62c45b05f8fbff166517b)
---
 src/udp6.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/udp6.c b/src/udp6.c
index fdd8089..236b962 100644
--- a/src/udp6.c
+++ b/src/udp6.c
@@ -29,7 +29,10 @@ void udp6_input(struct mbuf *m)
     ip = mtod(m, struct ip6 *);
     m->m_len -= iphlen;
     m->m_data += iphlen;
-    uh = mtod(m, struct udphdr *);
+    uh = mtod_check(m, sizeof(struct udphdr));
+    if (uh == NULL) {
+        goto bad;
+    }
     m->m_len += iphlen;
     m->m_data -= iphlen;
 
-- 
2.29.0