netdev - [PATCH] net: core: devlink.c: Hold devlink->lock from the beginning of devlink_dpipe_table

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Message-Id: <20200223112233.13417-1-madhuparnabhowmik10@gmail.com>
Date:   Sun, 23 Feb 2020 16:52:33 +0530
From:   madhuparnabhowmik10@...il.com
To:     jiri@...lanox.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@...lfernandes.org,
        linux-kernel-mentees@...ts.linuxfoundation.org, paulmck@...nel.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH] net: core: devlink.c: Hold devlink->lock from the beginning of devlink_dpipe_table_register()

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

devlink_dpipe_table_find() should be called under either
rcu_read_lock() or devlink->lock. devlink_dpipe_table_register()
calls devlink_dpipe_table_find() without holding the lock
and acquires it later. Therefore hold the devlink->lock
from the beginning of devlink_dpipe_table_register().

Suggested-by: Jiri Pirko <jiri@...lanox.com>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 net/core/devlink.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 4c63c9a4c09e..e82750bdc496 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -6838,26 +6838,33 @@ int devlink_dpipe_table_register(struct devlink *devlink,
 				 void *priv, bool counter_control_extern)
 {
 	struct devlink_dpipe_table *table;
-
-	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name))
-		return -EEXIST;
+	int err = 0;
 
 	if (WARN_ON(!table_ops->size_get))
 		return -EINVAL;
 
+	mutex_lock(&devlink->lock);
+
+	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name)) {
+		err = -EEXIST;
+		goto unlock;
+	}
+
 	table = kzalloc(sizeof(*table), GFP_KERNEL);
-	if (!table)
-		return -ENOMEM;
+	if (!table) {
+		err = -ENOMEM;
+		goto unlock;
+	}
 
 	table->name = table_name;
 	table->table_ops = table_ops;
 	table->priv = priv;
 	table->counter_control_extern = counter_control_extern;
 
-	mutex_lock(&devlink->lock);
 	list_add_tail_rcu(&table->list, &devlink->dpipe_table_list);
+unlock:
 	mutex_unlock(&devlink->lock);
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL_GPL(devlink_dpipe_table_register);
 
-- 
2.17.1