[PATCH 4.15 047/122] netlink: ensure to loop over all netns in genlmsg_multicast_allns()

[Greg Kroah-Hartman]

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

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

From: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>


[ Upstream commit cb9f7a9a5c96a773bbc9c70660dc600cfff82f82 ]

Nowadays, nlmsg_multicast() returns only 0 or -ESRCH but this was not the
case when commit 134e63756d5f was pushed.
However, there was no reason to stop the loop if a netns does not have
listeners.
Returns -ESRCH only if there was no listeners in all netns.

To avoid having the same problem in the future, I didn't take the
assumption that nlmsg_multicast() returns only 0 or -ESRCH.

Fixes: 134e63756d5f ("genetlink: make netns aware")
CC: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/netlink/genetlink.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1081,6 +1081,7 @@ static int genlmsg_mcast(struct sk_buff
 {
 	struct sk_buff *tmp;
 	struct net *net, *prev = NULL;
+	bool delivered = false;
 	int err;
 
 	for_each_net_rcu(net) {
@@ -1092,14 +1093,21 @@ static int genlmsg_mcast(struct sk_buff
 			}
 			err = nlmsg_multicast(prev->genl_sock, tmp,
 					      portid, group, flags);
-			if (err)
+			if (!err)
+				delivered = true;
+			else if (err != -ESRCH)
 				goto error;
 		}
 
 		prev = net;
 	}
 
-	return nlmsg_multicast(prev->genl_sock, skb, portid, group, flags);
+	err = nlmsg_multicast(prev->genl_sock, skb, portid, group, flags);
+	if (!err)
+		delivered = true;
+	else if (err != -ESRCH)
+		goto error;
+	return delivered ? 0 : -ESRCH;
  error:
 	kfree_skb(skb);
 	return err;