[bug report] ASoC: SOF: ipc-msg-injector: Separate the message sending

[Dan Carpenter]

Hello Peter Ujfalusi,

The patch a9aa3381e404: "ASoC: SOF: ipc-msg-injector: Separate the
message sending" from May 6, 2022, leads to the following Smatch
static checker warning:

	sound/soc/sof/sof-client-ipc-msg-injector.c:162 sof_msg_inject_dfs_write()
	warn: kernel error codes cast to unsigned 'size'

sound/soc/sof/sof-client-ipc-msg-injector.c
    148 static ssize_t sof_msg_inject_dfs_write(struct file *file, const char __user *buffer,
    149                                         size_t count, loff_t *ppos)
    150 {
    151         struct sof_client_dev *cdev = file->private_data;
    152         struct sof_msg_inject_priv *priv = cdev->data;
    153         size_t size;
    154         int ret;
    155 
    156         if (*ppos)
    157                 return 0;

I think there needs to be an "if (count != priv->max_msg_size)" check
or something.  Or another option would be the do a memset()

	memset(priv->tx_buffer, 0, priv->max_msg_size);

before the simple_write_to_buffer().  Otherwise if count == 1 then we
re-use stale data.

    158 
    159         size = simple_write_to_buffer(priv->tx_buffer, priv->max_msg_size,
    160                                       ppos, buffer, count);
    161         if (size != count)
--> 162                 return size > 0 ? -EFAULT : size;
    163 
    164         memset(priv->rx_buffer, 0, priv->max_msg_size);
    165 
    166         ret = sof_msg_inject_send_message(cdev);
    167 
    168         /* return the error code if test failed */
    169         if (ret < 0)
    170                 size = ret;
    171 
    172         return size;
    173 };

regards,
dan carpenter