From 49badf39a1454eae6a4f72ac9b735b70a5366390 Mon Sep 17 00:00:00 2001
From: Dirk Ziegelmeier <dirk@ziegelmeier.net>
Date: Fri, 29 Apr 2016 11:16:33 +0200
Subject: [PATCH] Fix bug #47805: dhcp_recv can dereference NULL pointer

---
 src/core/ipv4/dhcp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/core/ipv4/dhcp.c b/src/core/ipv4/dhcp.c
index e0b78178..3c146755 100644
--- a/src/core/ipv4/dhcp.c
+++ b/src/core/ipv4/dhcp.c
@@ -1737,8 +1737,11 @@ dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr,
     /* remember offered lease */
     dhcp_handle_offer(netif);
   }
+
 free_pbuf_and_return:
-  dhcp->msg_in = NULL;
+  if(dhcp != NULL) {
+    dhcp->msg_in = NULL;
+  }
   pbuf_free(p);
 }