packet: only test po->has_vnet_hdr once in packet_snd

[ Upstream commit da7c9561015e93d10fe6aab73e9288e0d09d65a6 ]

Packet socket option po->has_vnet_hdr can be updated concurrently with
other operations if no ring is attached.

Do not test the option twice in packet_snd, as the value may change in
between calls. A race on setsockopt disable may cause a packet > mtu
to be sent without having GSO options set.

Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a018f437a8fd372a2559dcaa634c116d00114655..241f69039a72192bd7f9b5e2ce8348bc16af9a3c 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1717,7 +1717,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
        }
        spin_unlock(&po->bind_lock);
 
-       if (err && !refcount_read(&match->sk_ref)) {
+       if (err && !atomic_read(&match->sk_ref)) {
                list_del(&match->list);
                kfree(match);
        }
@@ -2656,6 +2656,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
        int vnet_hdr_len;
        struct packet_sock *po = pkt_sk(sk);
        unsigned short gso_type = 0;
+       bool has_vnet_hdr = false;
        int hlen, tlen, linear;
        int extra_len = 0;
        ssize_t n;
@@ -2743,6 +2744,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
                                goto out_unlock;
 
                }
+               has_vnet_hdr = true;
        }
 
        if (unlikely(sock_flag(sk, SOCK_NOFCS))) {
@@ -2802,7 +2804,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 
        packet_pick_tx_queue(dev, skb);
 
-       if (po->has_vnet_hdr) {
+       if (has_vnet_hdr) {
                if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                        u16 s = __virtio16_to_cpu(vio_le(), vnet_hdr.csum_start);
                        u16 o = __virtio16_to_cpu(vio_le(), vnet_hdr.csum_offset);