netdev - [PATCH v2 2/3] net: Add BUG_ON() to get

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Message-ID: <151551003602.4318.8752010178458260165.stgit@localhost.localdomain>
Date:   Tue, 09 Jan 2018 18:00:40 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     eric.dumazet@...il.com, ktkhai@...tuozzo.com, ebiederm@...ssion.com
Subject: [PATCH v2 2/3] net: Add BUG_ON() to get_net()

Since people may mistakenly obtain destroying net
from net_namespace_list and from net::netns_ids
without checking for its net::counter, let's protect
against such situations and insert BUG_ON() to stop
move on after this.

Panic is better, than memory corruption and undefined
behavior.

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 include/net/net_namespace.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 10f99dafd5ac..ff0e47471d5b 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -195,7 +195,7 @@ void __put_net(struct net *net);
 
 static inline struct net *get_net(struct net *net)
 {
-	atomic_inc(&net->count);
+	BUG_ON(atomic_inc_return(&net->count) <= 1);
 	return net;
 }