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From:   Christian Marangi <ansuelsmth@gmail.com>
To:     Pavel Machek <pavel@ucw.cz>, Lee Jones <lee@kernel.org>,
        Andrew Lunn <andrew@lunn.ch>,
        Christian Marangi <ansuelsmth@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Li Zetao <lizetao1@huawei.com>, linux-leds@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org, kernel test robot <lkp@intel.com>
Subject: [net PATCH] leds: trigger: netdev: move size check in set_device_name
Date:   Sat,  7 Oct 2023 15:10:42 +0200
Message-Id: <20231007131042.15032-1-ansuelsmth@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

GCC 13.2 complains about array subscript 17 is above array bounds of
'char[16]' with IFNAMSIZ set to 16.

The warning is correct but this scenario is impossible.
set_device_name is called by device_name_store (store sysfs entry) and
netdev_trig_activate.

device_name_store already check if size is >= of IFNAMSIZ and return
-EINVAL. (making the warning scenario impossible)

netdev_trig_activate works on already defined interface, where the name
has already been checked and should already follow the condition of
strlen() < IFNAMSIZ.

Aside from the scenario being impossible, set_device_name can be
improved to both mute the warning and make the function safer.
To make it safer, move size check from device_name_store directly to
set_device_name and prevent any out of bounds scenario.

Cc: stable@vger.kernel.org
Fixes: 28a6a2ef18ad ("leds: trigger: netdev: refactor code setting device name")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309192035.GTJEEbem-lkp@intel.com/
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/leds/trigger/ledtrig-netdev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 58f3352539e8..e358e77e4b38 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -221,6 +221,9 @@ static ssize_t device_name_show(struct device *dev,
 static int set_device_name(struct led_netdev_data *trigger_data,
 			   const char *name, size_t size)
 {
+	if (size >= IFNAMSIZ)
+		return -EINVAL;
+
 	cancel_delayed_work_sync(&trigger_data->work);
 
 	mutex_lock(&trigger_data->lock);
@@ -263,9 +266,6 @@ static ssize_t device_name_store(struct device *dev,
 	struct led_netdev_data *trigger_data = led_trigger_get_drvdata(dev);
 	int ret;
 
-	if (size >= IFNAMSIZ)
-		return -EINVAL;
-
 	ret = set_device_name(trigger_data, buf, size);
 
 	if (ret < 0)
-- 
2.40.1