udp: check upd_input buffer size

Git-commit: 74572be49247c8c5feae7c6e0b50c4f569ca9824
References: bsc#1187367, CVE-2021-3594

Fixes: CVE-2021-3594
Fixes: https://gitlab.freedesktop.org/slirp/libslirp/-/issues/47
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Jose R Ziviani <jose.ziviani@suse.com>

diff --git a/slirp/src/udp.c b/slirp/src/udp.c
index 6bde20fafab5695eedd48eb3759068049f8e9e92..c2d2f40b10880ccf677b5f10bb75cfe3b54f5641 100644 (file)
--- a/slirp/src/udp.c
+++ b/slirp/src/udp.c
@@ -90,7 +90,10 @@ 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);
 
     /*