net: Convert atomic_t net::count to refcount_t

Since net could be obtained from RCU lists,
and there is a race with net destruction,
the patch converts net::count to refcount_t.

This provides sanity checks for the cases of
incrementing counter of already dead net,
when maybe_get_net() has to used instead
of get_net().

Drivers: allyesconfig and allmodconfig are OK.

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 10f99dafd5ac..f8a84a2c2341 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -51,7 +51,7 @@ struct net {
 	refcount_t		passive;	/* To decided when the network
 						 * namespace should be freed.
 						 */
-	atomic_t		count;		/* To decided when the network
+	refcount_t		count;		/* To decided when the network
 						 *  namespace should be shut down.
 						 */
 	spinlock_t		rules_mod_lock;
@@ -195,7 +195,7 @@ void __put_net(struct net *net);
 
 static inline struct net *get_net(struct net *net)
 {
-	atomic_inc(&net->count);
+	refcount_inc(&net->count);
 	return net;
 }
 
@@ -206,14 +206,14 @@ static inline struct net *maybe_get_net(struct net *net)
 	 * exists.  If the reference count is zero this
 	 * function fails and returns NULL.
 	 */
-	if (!atomic_inc_not_zero(&net->count))
+	if (!refcount_inc_not_zero(&net->count))
 		net = NULL;
 	return net;
 }
 
 static inline void put_net(struct net *net)
 {
-	if (atomic_dec_and_test(&net->count))
+	if (refcount_dec_and_test(&net->count))
 		__put_net(net);
 }