netlink: correct nlmsg size for multicast notifications

Corrected the netlink message size calculation for multicast group
join/leave notifications. The previous calculation did not account for
the inclusion of both IPv4/IPv6 addresses and ifa_cacheinfo in the
payload. This fix ensures that the allocated message size is
sufficient to hold all necessary information.

This patch also includes the following improvements:
* Uses GFP_KERNEL instead of GFP_ATOMIC when holding the RTNL mutex.
* Uses nla_total_size(sizeof(struct in6_addr)) instead of
  nla_total_size(16).
* Removes unnecessary EXPORT_SYMBOL().

Fixes: 2c2b61d ("netlink: add IGMP/MLD join/leave notifications")
Cc: Maciej Żenczykowski <[email protected]>
Cc: Lorenzo Colitti <[email protected]>
Signed-off-by: Yuyang Huang <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Yuyang Huang

net/ipv4/igmp.c

@@ -1473,7 +1473,9 @@ static void inet_ifmcaddr_notify(struct net_device *dev,
 	int err = -ENOMEM;
 
 	skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
-			nla_total_size(sizeof(__be32)), GFP_ATOMIC);
+			nla_total_size(sizeof(__be32)) +
+			nla_total_size(sizeof(struct ifa_cacheinfo)),
+			GFP_KERNEL);
 	if (!skb)
 		goto error;
 
@@ -1484,7 +1486,7 @@ static void inet_ifmcaddr_notify(struct net_device *dev,
 		goto error;
 	}
 
-	rtnl_notify(skb, net, 0, RTNLGRP_IPV4_MCADDR, NULL, GFP_ATOMIC);
+	rtnl_notify(skb, net, 0, RTNLGRP_IPV4_MCADDR, NULL, GFP_KERNEL);
 	return;
 error:
 	rtnl_set_sk_err(net, RTNLGRP_IPV4_MCADDR, err);

net/ipv6/addrconf.c

@@ -5239,7 +5239,6 @@ int inet6_fill_ifmcaddr(struct sk_buff *skb,
 	nlmsg_end(skb, nlh);
 	return 0;
 }
-EXPORT_SYMBOL(inet6_fill_ifmcaddr);
 
 static int inet6_fill_ifacaddr(struct sk_buff *skb,
 			       const struct ifacaddr6 *ifaca,

net/ipv6/mcast.c

@@ -920,7 +920,9 @@ static void inet6_ifmcaddr_notify(struct net_device *dev,
 	int err = -ENOMEM;
 
 	skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
-			nla_total_size(16), GFP_ATOMIC);
+			nla_total_size(sizeof(struct in6_addr)) +
+			nla_total_size(sizeof(struct ifa_cacheinfo)),
+			GFP_KERNEL);
 	if (!skb)
 		goto error;
 
@@ -931,7 +933,7 @@ static void inet6_ifmcaddr_notify(struct net_device *dev,
 		goto error;
 	}
 
-	rtnl_notify(skb, net, 0, RTNLGRP_IPV6_MCADDR, NULL, GFP_ATOMIC);
+	rtnl_notify(skb, net, 0, RTNLGRP_IPV6_MCADDR, NULL, GFP_KERNEL);
 	return;
 error:
 	rtnl_set_sk_err(net, RTNLGRP_IPV6_MCADDR, err);