[PATCH net-next 4/9] sit: annotate data-races around tunnel->fwmark

[Eric Dumazet <edumazet@google.com>]

ipip6_tunnel_xmit() runs locklessly (dev->lltx == true) and reads
tunnel->fwmark.

In preparation for converting ipip6_fill_info() to run without RTNL,
add READ_ONCE() and WRITE_ONCE() annotations around tunnel->fwmark.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv6/sit.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 9a2bbd76d3794849cd11c6530ba1303bf53fa388..e85fa80e80d1ad2c593b860685b9f5bac21e66d9 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -929,7 +929,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 	if (!dst && !ipip6_tunnel_dst_find(skb, &dst, false))
 		goto tx_error;
 
-	flowi4_init_output(&fl4, tunnel->parms.link, tunnel->fwmark,
+	flowi4_init_output(&fl4, tunnel->parms.link, READ_ONCE(tunnel->fwmark),
 			   tos & INET_DSCP_MASK, RT_SCOPE_UNIVERSE,
 			   IPPROTO_IPV6, 0, dst, tiph->saddr, 0, 0,
 			   sock_net_uid(tunnel->net, NULL));
@@ -1153,7 +1153,7 @@ static void ipip6_tunnel_update(struct ip_tunnel *t,
 	t->parms.iph.frag_off = p->iph.frag_off;
 	if (t->parms.link != p->link || t->fwmark != fwmark) {
 		t->parms.link = p->link;
-		t->fwmark = fwmark;
+		WRITE_ONCE(t->fwmark, fwmark);
 		ipip6_tunnel_bind_dev(t->dev);
 	}
 	dst_cache_reset(&t->dst_cache);
@@ -1706,7 +1706,7 @@ static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	    nla_put_u8(skb, IFLA_IPTUN_PROTO, parm->iph.protocol) ||
 	    nla_put_be16(skb, IFLA_IPTUN_FLAGS,
 			 ip_tunnel_flags_to_be16(parm->i_flags)) ||
-	    nla_put_u32(skb, IFLA_IPTUN_FWMARK, tunnel->fwmark))
+	    nla_put_u32(skb, IFLA_IPTUN_FWMARK, READ_ONCE(tunnel->fwmark)))
 		goto nla_put_failure;
 
 #ifdef CONFIG_IPV6_SIT_6RD
-- 
2.55.0.979.g7e5102b832-goog