3 files changed, 6 insertions, 2 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index c29d75d8f1b1..090e9991ac2a 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1304,7 +1304,9 @@ static void arp_format_neigh_entry(struct seq_file *seq,
                 hbuffer[k++] = hex_asc_lo(n->ha[j]);
                 hbuffer[k++] = ':';
         }
-        hbuffer[--k] = 0;
+        if (k != 0)
+                --k;
+        hbuffer[k] = 0;
 #if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
         }
 #endif
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index cb4a0f4bd5e5..82c11dd10a62 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -951,7 +951,7 @@ static int ipgre_tunnel_bind_dev(struct net_device *dev)
                         addend += 4;
         }
         dev->needed_headroom = addend + hlen;
-        mtu -= dev->hard_header_len - addend;
+        mtu -= dev->hard_header_len + addend;
 
         if (mtu < 68)
                 mtu = 68;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 7d0821054729..7ffcd96fe591 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -813,6 +813,8 @@ int ip_append_data(struct sock *sk,
                         inet->cork.addr = ipc->addr;
                 }
                 rt = *rtp;
+                if (unlikely(!rt))
+                        return -EFAULT;
                 /*
                  * We steal reference to this route, caller should not release it
                  */