packet: validate variable length ll headers

Replace link layer header validation check ll_header_truncate with
more generic dev_validate_header.

Validation based on hard_header_len incorrectly drops valid packets
in variable length protocols, such as AX25. dev_validate_header
calls header_ops.validate for such protocols to ensure correctness
below hard_header_len.

See also http://comments.gmane.org/gmane.linux.network/401064

Fixes 9c7077622dd9 ("packet: make packet_snd fail on len smaller than l2 header")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d41b107..1ecfa71 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1915,6 +1915,10 @@ retry:
                goto retry;
        }
 
+       if (!dev_validate_header(dev, skb->data, len)) {
+               err = -EINVAL;
+               goto out_unlock;
+       }
        if (len > (dev->mtu + dev->hard_header_len + extra_len) &&
            !packet_extra_vlan_len_allowed(dev, skb)) {
                err = -EMSGSIZE;
@@ -2393,18 +2397,6 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
        sock_wfree(skb);
 }
 
-static bool ll_header_truncated(const struct net_device *dev, int len)
-{
-       /* net device doesn't like empty head */
-       if (unlikely(len < dev->hard_header_len)) {
-               net_warn_ratelimited("%s: packet size is too short (%d < %d)\n",
-                                    current->comm, len, dev->hard_header_len);
-               return true;
-       }
-
-       return false;
-}
-
 static void tpacket_set_protocol(const struct net_device *dev,
                                 struct sk_buff *skb)
 {
@@ -2522,16 +2514,20 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                if (unlikely(err < 0))
                        return -EINVAL;
        } else if (copylen) {
+               int hdrlen = min_t(int, copylen, tp_len);
+
                skb_push(skb, dev->hard_header_len);
                skb_put(skb, copylen - dev->hard_header_len);
-               err = skb_store_bits(skb, 0, data, copylen);
+               err = skb_store_bits(skb, 0, data, hdrlen);
                if (unlikely(err))
                        return err;
+               if (!dev_validate_header(dev, skb->data, hdrlen))
+                       return -EINVAL;
                if (!skb->protocol)
                        tpacket_set_protocol(dev, skb);
 
-               data += copylen;
-               to_write -= copylen;
+               data += hdrlen;
+               to_write -= hdrlen;
        }
 
        offset = offset_in_page(data);
@@ -2703,13 +2699,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
                        copylen = __virtio16_to_cpu(vio_le(),
                                                    vnet_hdr->hdr_len);
                }
-               if (dev->hard_header_len) {
-                       if (ll_header_truncated(dev, tp_len)) {
-                               tp_len = -EINVAL;
-                               goto tpacket_error;
-                       }
-                       copylen = max_t(int, copylen, dev->hard_header_len);
-               }
+               copylen = max_t(int, copylen, dev->hard_header_len);
                skb = sock_alloc_send_skb(&po->sk,
                                hlen + tlen + sizeof(struct sockaddr_ll) +
                                (copylen - dev->hard_header_len),
@@ -2905,9 +2895,6 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
                offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len);
                if (unlikely(offset < 0))
                        goto out_free;
-       } else {
-               if (ll_header_truncated(dev, len))
-                       goto out_free;
        }
 
        /* Returns -EFAULT on error */
@@ -2915,6 +2902,12 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
        if (err)
                goto out_free;
 
+       if (sock->type == SOCK_RAW &&
+           !dev_validate_header(dev, skb->data, len)) {
+               err = -EINVAL;
+               goto out_free;
+       }
+
        sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
 
        if (!vnet_hdr.gso_type && (len > dev->mtu + reserve + extra_len) &&