packet: only test po->has_vnet_hdr once in packet_snd

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>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a10c2836465cf499e2b723419da25bc3ad07d69f..bec01a3daf5b02bd716dbff5c9efef8d6a7982be 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2840,6 +2840,7 @@ 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;
 
@@ -2883,6 +2884,7 @@ 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)
        skb->priority = sk->sk_priority;
        skb->mark = sockc.mark;
 
-       if (po->has_vnet_hdr) {
+       if (has_vnet_hdr) {
                err = virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le());
                if (err)
                        goto out_free;