ipv6: annotate data-races around devconf->rpl_seg_enabled

devconf->rpl_seg_enabled can be changed concurrently from
/proc/sys/net/ipv6/conf, annotate lockless reads on it.

Signed-off-by: Yue Haibing <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Yue Haibing

net/ipv6/exthdrs.c

@@ -494,10 +494,8 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 
 	idev = __in6_dev_get(skb->dev);
 
-	accept_rpl_seg = net->ipv6.devconf_all->rpl_seg_enabled;
-	if (accept_rpl_seg > idev->cnf.rpl_seg_enabled)
-		accept_rpl_seg = idev->cnf.rpl_seg_enabled;
-
+	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
+			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 	if (!accept_rpl_seg) {
 		kfree_skb(skb);
 		return -1;