From ca41f7eaa58d3f63a3df58d812b3cec32343ab6a 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 16:40:23 +0400
Subject: [PATCH 7/7] udp: check upd_input buffer size
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Fixes: CVE-2021-3594
Fixes: https://gitlab.freedesktop.org/slirp/libslirp/-/issues/47

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
(cherry picked from commit 74572be49247c8c5feae7c6e0b50c4f569ca9824)
---
 src/udp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/udp.c b/src/udp.c
index 050cee4..e4578aa 100644
--- a/src/udp.c
+++ b/src/udp.c
@@ -94,7 +94,10 @@ void udp_input(register struct mbuf *m, int iphlen)
     /*
      * Get IP and UDP header together in first mbuf.
      */
-    ip = mtod(m, struct ip *);
+    ip = mtod_check(m, iphlen + sizeof(struct udphdr));
+    if (ip == NULL) {
+        goto bad;
+    }
     uh = (struct udphdr *)((char *)ip + iphlen);
 
     /*
-- 
2.29.0