[PATCH v1 net-next 09/14] bareudp: Protect bareudp_list with mutex.

[Kuniyuki Iwashima <kuniyu@google.com>]

struct bareudp_dev.net is the netns where the backend bareudp
socket resides.

struct bareudp_dev is linked to the bareudp_net.bareudp_list of
the socket's netns.

During netns dismantle or module unload, bareudp_exit_rtnl_net()
iterates the list and queues devices for destruction regardless
of the devices' netns.

Thus, once RTNL is removed, the list can be modified concurrently
from different netns due to device removal.

Let's protect it with per-netns mutex.

bareudp_newlink() is still protected by rtnl_net_lock()s, so
acquiring gn->lock twice in bareudp_find_dev() and
bareudp_configure() is not a problem.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 drivers/net/bareudp.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index 5ef841c85526..7dedf4867e7b 100644
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -36,6 +36,7 @@ static unsigned int bareudp_net_id;
 
 struct bareudp_net {
 	struct list_head        bareudp_list;
+	struct mutex		lock;
 };
 
 struct bareudp_conf {
@@ -636,10 +637,15 @@ static struct bareudp_dev *bareudp_find_dev(struct bareudp_net *bn,
 {
 	struct bareudp_dev *bareudp, *t = NULL;
 
+	mutex_lock(&bn->lock);
+
 	list_for_each_entry(bareudp, &bn->bareudp_list, next) {
 		if (conf->port == bareudp->port)
 			t = bareudp;
 	}
+
+	mutex_unlock(&bn->lock);
+
 	return t;
 }
 
@@ -675,7 +681,10 @@ static int bareudp_configure(struct net *net, struct net_device *dev,
 	if (err)
 		return err;
 
+	mutex_lock(&bn->lock);
 	list_add(&bareudp->next, &bn->bareudp_list);
+	mutex_unlock(&bn->lock);
+
 	return 0;
 }
 
@@ -692,7 +701,7 @@ static int bareudp_link_config(struct net_device *dev,
 	return 0;
 }
 
-static void bareudp_dellink(struct net_device *dev, struct list_head *head)
+static void __bareudp_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct bareudp_dev *bareudp = netdev_priv(dev);
 
@@ -700,6 +709,18 @@ static void bareudp_dellink(struct net_device *dev, struct list_head *head)
 	unregister_netdevice_queue(dev, head);
 }
 
+static void bareudp_dellink(struct net_device *dev, struct list_head *head)
+{
+	struct bareudp_dev *bareudp = netdev_priv(dev);
+	struct bareudp_net *bn;
+
+	bn = net_generic(bareudp->net, bareudp_net_id);
+
+	mutex_lock(&bn->lock);
+	__bareudp_dellink(dev, head);
+	mutex_unlock(&bn->lock);
+}
+
 static int bareudp_newlink(struct net_device *dev,
 			   struct rtnl_newlink_params *params,
 			   struct netlink_ext_ack *extack)
@@ -776,6 +797,8 @@ static __net_init int bareudp_init_net(struct net *net)
 	struct bareudp_net *bn = net_generic(net, bareudp_net_id);
 
 	INIT_LIST_HEAD(&bn->bareudp_list);
+	mutex_init(&bn->lock);
+
 	return 0;
 }
 
@@ -785,8 +808,12 @@ static void __net_exit bareudp_exit_rtnl_net(struct net *net,
 	struct bareudp_net *bn = net_generic(net, bareudp_net_id);
 	struct bareudp_dev *bareudp, *next;
 
+	mutex_lock(&bn->lock);
+
 	list_for_each_entry_safe(bareudp, next, &bn->bareudp_list, next)
-		bareudp_dellink(bareudp->dev, dev_kill_list);
+		__bareudp_dellink(bareudp->dev, dev_kill_list);
+
+	mutex_unlock(&bn->lock);
 }
 
 static struct pernet_operations bareudp_net_ops = {
-- 
2.55.0.rc0.799.gd6f94ed593-goog