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