net: hns3: add input length check for debugfs write function

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

If the input length reaches the maximum value of size_t, the reverse is
triggered when 1 is added. In addition, there is no need to have such a
large length. Therefore, the input length should be checked and the value
should be less than or equal to 1024.

Feature or Bugfix:Bugfix
Signed-off-by: NYufeng Mo <moyufeng@huawei.com>
Reviewed-by: Nlipeng <lipeng321@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c

@@ -8,6 +8,7 @@
 #include "hns3_enet.h"
 
 #define HNS3_DBG_READ_LEN 256
+#define HNS3_DBG_WRITE_LEN 1024
 
 static struct dentry *hns3_dbgfs_root;
 
@@ -320,6 +321,9 @@ static ssize_t hns3_dbg_cmd_write(struct file *filp, const char __user *buffer,
 	    test_bit(HNS3_NIC_STATE_RESETTING, &priv->state))
 		return 0;
 
+	if (count > HNS3_DBG_WRITE_LEN)
+		return 0;
+
 	cmd_buf = kzalloc(count + 1, GFP_KERNEL);
 	if (!cmd_buf)
 		return count;