Commit 9ed988cd authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

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 9c707762 ("packet: make packet_snd fail on len smaller than l2 header")
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ea47781c

net/packet/af_packet.c

+18 −25
Original line number Diff line number Diff line
@@ -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);

		}

		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) &&

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