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Subject[PATCH 4.2 12/61] packet: only allow extra vlan len on ethernet devices
Date
4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@iogearbox.net>

[ Upstream commit 3c70c132488794e2489ab045559b0ce0afcf17de ]

Packet sockets can be used by various net devices and are not
really restricted to ARPHRD_ETHER device types. However, when
currently checking for the extra 4 bytes that can be transmitted
in VLAN case, our assumption is that we generally probe on
ARPHRD_ETHER devices. Therefore, before looking into Ethernet
header, check the device type first.

This also fixes the issue where non-ARPHRD_ETHER devices could
have no dev->hard_header_len in TX_RING SOCK_RAW case, and thus
the check would test unfilled linear part of the skb (instead
of non-linear).

Fixes: 57f89bfa2140 ("network: Allow af_packet to transmit +4 bytes for VLAN packets.")
Fixes: 52f1454f629f ("packet: allow to transmit +4 byte in TX_RING slot for VLAN case")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/packet/af_packet.c | 60 ++++++++++++++++++++-----------------------------
1 file changed, 25 insertions(+), 35 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1622,6 +1622,20 @@ static void fanout_release(struct sock *
kfree_rcu(po->rollover, rcu);
}

+static bool packet_extra_vlan_len_allowed(const struct net_device *dev,
+ struct sk_buff *skb)
+{
+ /* Earlier code assumed this would be a VLAN pkt, double-check
+ * this now that we have the actual packet in hand. We can only
+ * do this check on Ethernet devices.
+ */
+ if (unlikely(dev->type != ARPHRD_ETHER))
+ return false;
+
+ skb_reset_mac_header(skb);
+ return likely(eth_hdr(skb)->h_proto == htons(ETH_P_8021Q));
+}
+
static const struct proto_ops packet_ops;

static const struct proto_ops packet_ops_spkt;
@@ -1783,18 +1797,10 @@ retry:
goto retry;
}

- if (len > (dev->mtu + dev->hard_header_len + extra_len)) {
- /* Earlier code assumed this would be a VLAN pkt,
- * double-check this now that we have the actual
- * packet in hand.
- */
- struct ethhdr *ehdr;
- skb_reset_mac_header(skb);
- ehdr = eth_hdr(skb);
- if (ehdr->h_proto != htons(ETH_P_8021Q)) {
- err = -EMSGSIZE;
- goto out_unlock;
- }
+ if (len > (dev->mtu + dev->hard_header_len + extra_len) &&
+ !packet_extra_vlan_len_allowed(dev, skb)) {
+ err = -EMSGSIZE;
+ goto out_unlock;
}

skb->protocol = proto;
@@ -2406,18 +2412,10 @@ static int tpacket_snd(struct packet_soc
tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
addr, hlen);
if (likely(tp_len >= 0) &&
- tp_len > dev->mtu + dev->hard_header_len) {
- struct ethhdr *ehdr;
- /* Earlier code assumed this would be a VLAN pkt,
- * double-check this now that we have the actual
- * packet in hand.
- */
+ tp_len > dev->mtu + dev->hard_header_len &&
+ !packet_extra_vlan_len_allowed(dev, skb))
+ tp_len = -EMSGSIZE;

- skb_reset_mac_header(skb);
- ehdr = eth_hdr(skb);
- if (ehdr->h_proto != htons(ETH_P_8021Q))
- tp_len = -EMSGSIZE;
- }
if (unlikely(tp_len < 0)) {
if (po->tp_loss) {
__packet_set_status(po, ph,
@@ -2638,18 +2636,10 @@ static int packet_snd(struct socket *soc

sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);

- if (!gso_type && (len > dev->mtu + reserve + extra_len)) {
- /* Earlier code assumed this would be a VLAN pkt,
- * double-check this now that we have the actual
- * packet in hand.
- */
- struct ethhdr *ehdr;
- skb_reset_mac_header(skb);
- ehdr = eth_hdr(skb);
- if (ehdr->h_proto != htons(ETH_P_8021Q)) {
- err = -EMSGSIZE;
- goto out_free;
- }
+ if (!gso_type && (len > dev->mtu + reserve + extra_len) &&
+ !packet_extra_vlan_len_allowed(dev, skb)) {
+ err = -EMSGSIZE;
+ goto out_free;
}

skb->protocol = proto;



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