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

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Date:   Sun, 23 Feb 2020 16:26:10 +0530
From:   Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     madhuparnabhowmik10@...il.com, jiri@...lanox.com,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, joel@...lfernandes.org,
        frextrite@...il.com,
        linux-kernel-mentees@...ts.linuxfoundation.org, paulmck@...nel.org
Subject: Re: [PATCH] net: core: devlink.c: Hold devlink->lock from the
 beginning of devlink_dpipe_table_register()

On Sun, Feb 23, 2020 at 07:43:29AM +0100, Jiri Pirko wrote:
> Sat, Feb 22, 2020 at 07:52:34AM CET, madhuparnabhowmik10@...il.com wrote:
> >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 | 15 +++++++++++----
> > 1 file changed, 11 insertions(+), 4 deletions(-)
> >
> >diff --git a/net/core/devlink.c b/net/core/devlink.c
> >index 3e8c94155d93..ba9dd8cb98c3 100644
> >--- a/net/core/devlink.c
> >+++ b/net/core/devlink.c
> >@@ -6840,22 +6840,29 @@ int devlink_dpipe_table_register(struct devlink *devlink,
> > {
> > 	struct devlink_dpipe_table *table;
> > 
> >-	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name))
> >+	mutex_lock(&devlink->lock);
> >+
> >+	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name)) {
> >+		mutex_unlock(&devlink->lock);
> > 		return -EEXIST;
> >+	}
> > 
> >-	if (WARN_ON(!table_ops->size_get))
> >+	if (WARN_ON(!table_ops->size_get)) {
> >+		mutex_unlock(&devlink->lock);
> > 		return -EINVAL;
> >+	}
> > 
> > 	table = kzalloc(sizeof(*table), GFP_KERNEL);
> >-	if (!table)
> >+	if (!table) {
> >+		mutex_unlock(&devlink->lock);
> 
> Please use "goto unlock" instead of unlocking on multiple places.
>
Sure, I have sent a new patch.
Thank you,
Madhuparna
> 
> 
> > 		return -ENOMEM;
> >+	}
> > 
> > 	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);
> > 	mutex_unlock(&devlink->lock);
> > 	return 0;
> >-- 
> >2.17.1
> >