[PATCH 4.13 037/160] packet: only test po->has_vnet_hdr once in packet_snd

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

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

From: Willem de Bruijn <will...@google.com>


[ 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 <will...@google.com>
Reviewed-by: Eric Dumazet <eduma...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/packet/af_packet.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2842,6 +2842,7 @@ static int packet_snd(struct socket *soc
        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;
 
@@ -2885,6 +2886,7 @@ static int packet_snd(struct socket *soc
                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))) {
@@ -2943,7 +2945,7 @@ static int packet_snd(struct socket *soc
        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;