netdev - [PATCH v2 net-next 4/6] net: dsa: strip sysfs "tagging" string of trailing newline

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Date:   Tue, 15 Nov 2022 03:18:45 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Michael Walle <michael@...le.cc>,
        Heiko Thiery <heiko.thiery@...il.com>
Subject: [PATCH v2 net-next 4/6] net: dsa: strip sysfs "tagging" string of trailing newline

Currently, dsa_find_tagger_by_name() uses sysfs_streq() which works both
with strings that contain \n at the end (echo ocelot > .../dsa/tagging)
and with strings that don't (printf ocelot > .../dsa/tagging).

There will be a problem once we'll want to construct the modalias string
based on which we auto-load the protocol kernel module. If the sysfs
buffer ends in a newline, we need to strip it first. This is a
preparatory patch specifically for that.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
v1->v2: patch is new

 net/dsa/dsa.c      |  4 ++--
 net/dsa/dsa_priv.h |  2 +-
 net/dsa/master.c   | 13 ++++++++++++-
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 38c64cc5c0d2..e0ea5b309e61 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -78,7 +78,7 @@ const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops)
 /* Function takes a reference on the module owning the tagger,
  * so dsa_tag_driver_put must be called afterwards.
  */
-const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf)
+const struct dsa_device_ops *dsa_find_tagger_by_name(const char *name)
 {
 	const struct dsa_device_ops *ops = ERR_PTR(-ENOPROTOOPT);
 	struct dsa_tag_driver *dsa_tag_driver;
@@ -87,7 +87,7 @@ const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf)
 	list_for_each_entry(dsa_tag_driver, &dsa_tag_drivers_list, list) {
 		const struct dsa_device_ops *tmp = dsa_tag_driver->ops;
 
-		if (!sysfs_streq(buf, tmp->name))
+		if (strcmp(name, tmp->name))
 			continue;
 
 		if (!try_module_get(dsa_tag_driver->owner))
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index b4b8fe4ed9bf..9fe68d3ae2f5 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -245,7 +245,7 @@ struct dsa_slave_priv {
 /* dsa.c */
 const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol);
 void dsa_tag_driver_put(const struct dsa_device_ops *ops);
-const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf);
+const struct dsa_device_ops *dsa_find_tagger_by_name(const char *name);
 
 bool dsa_db_equal(const struct dsa_db *a, const struct dsa_db *b);
 
diff --git a/net/dsa/master.c b/net/dsa/master.c
index 40367ab41cf8..104eab880076 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -300,12 +300,23 @@ static ssize_t tagging_store(struct device *d, struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
 	const struct dsa_device_ops *new_tag_ops, *old_tag_ops;
+	const char *end = strchrnul(buf, '\n'), *name;
 	struct net_device *dev = to_net_dev(d);
 	struct dsa_port *cpu_dp = dev->dsa_ptr;
+	size_t len = end - buf;
 	int err;
 
+	/* Empty string passed */
+	if (!len)
+		return -ENOPROTOOPT;
+
+	name = kstrndup(buf, len, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+
 	old_tag_ops = cpu_dp->tag_ops;
-	new_tag_ops = dsa_find_tagger_by_name(buf);
+	new_tag_ops = dsa_find_tagger_by_name(name);
+	kfree(name);
 	/* Bad tagger name, or module is not loaded? */
 	if (IS_ERR(new_tag_ops))
 		return PTR_ERR(new_tag_ops);
-- 
2.34.1