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 0856c12..b17f909 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1713,7 +1713,7 @@ 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);
        }
@@ -2838,6 +2838,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
        struct virtio_net_hdr vnet_hdr = { 0 };
        int offset = 0;
        struct packet_sock *po = pkt_sk(sk);
+       bool has_vnet_hdr = false;
        int hlen, tlen, linear;
        int extra_len = 0;
 
@@ -2881,6 +2882,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
                err = packet_snd_vnet_parse(msg, &len, &vnet_hdr);
                if (err)
                        goto out_unlock;
+               has_vnet_hdr = true;
        }
 
        if (unlikely(sock_flag(sk, SOCK_NOFCS))) {
@@ -2941,7 +2943,7 @@ 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) {
                err = packet_snd_vnet_gso(skb, &vnet_hdr);
                if (err)
                        goto out_free;