Subject: [PATCH AUTOSEL 5.10 108/116] net: dsa: hold rtnl_mutex when calling dsa_master_{setup,teardown}

From: Sasha Levin <[email-masked]>
Date: Mon, 17 Jan 2022 21:39:59 -0500

From: Vladimir Oltean <[email-masked]>

[ Upstream commit c146f9bc195a9dc3ad7fd000a14540e7c9df952d ]

DSA needs to simulate master tracking events when a binding is first
with a DSA master established and torn down, in order to give drivers
the simplifying guarantee that ->master_state_change calls are made
only when the master's readiness state to pass traffic changes.
master_state_change() provide a operational bool that DSA driver can use
to understand if DSA master is operational or not.
To avoid races, we need to block the reception of
NETDEV_UP/NETDEV_CHANGE/NETDEV_GOING_DOWN events in the netdev notifier
chain while we are changing the master's dev->dsa_ptr (this changes what
netdev_uses_dsa(dev) reports).

The dsa_master_setup() and dsa_master_teardown() functions optionally
require the rtnl_mutex to be held, if the tagger needs the master to be
promiscuous, these functions call dev_set_promiscuity(). Move the
rtnl_lock() from that function and make it top-level.

Signed-off-by: Vladimir Oltean <[email-masked]>
Reviewed-by: Florian Fainelli <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 net/dsa/dsa2.c   | 8 ++++++++
 net/dsa/master.c | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index 71c8ef7d40870..d7cd7004a8e5d 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -577,6 +577,8 @@ static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
 	struct dsa_port *dp;
 	int err;
 
+	rtnl_lock();
+
 	list_for_each_entry(dp, &dst->ports, list) {
 		if (dsa_port_is_cpu(dp)) {
 			err = dsa_master_setup(dp->master, dp);
@@ -585,6 +587,8 @@ static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
 		}
 	}
 
+	rtnl_unlock();
+
 	return 0;
 }
 
@@ -592,9 +596,13 @@ static void dsa_tree_teardown_master(struct dsa_switch_tree *dst)
 {
 	struct dsa_port *dp;
 
+	rtnl_lock();
+
 	list_for_each_entry(dp, &dst->ports, list)
 		if (dsa_port_is_cpu(dp))
 			dsa_master_teardown(dp->master);
+
+	rtnl_unlock();
 }
 
 static int dsa_tree_setup(struct dsa_switch_tree *dst)
diff --git a/net/dsa/master.c b/net/dsa/master.c
index 45bd627b4e7bc..f9bc4233ca946 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -267,9 +267,9 @@ static void dsa_master_set_promiscuity(struct net_device *dev, int inc)
 	if (!ops->promisc_on_master)
 		return;
 
-	rtnl_lock();
+	ASSERT_RTNL();
+
 	dev_set_promiscuity(dev, inc);
-	rtnl_unlock();
 }
 
 static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
-- 
2.34.1