linux-kernel - [PATCH 4.4 24/36] netlink: ensure to loop over all netns in genlmsg_multicast

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Date:   Fri,  9 Mar 2018 16:18:40 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johannes Berg <johannes.berg@...el.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 24/36] netlink: ensure to loop over all netns in genlmsg_multicast_allns()

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

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

From: Nicolas Dichtel <nicolas.dichtel@...nd.com>


[ 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@...el.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/netlink/genetlink.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1118,6 +1118,7 @@ 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) {
@@ -1129,14 +1130,21 @@ 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;