[mfd] question about potential null pointer dereference

[Gustavo A. R. Silva]

Hello everybody,

While looking into Coverity ID 1408830 I ran into the following piece  
of code at drivers/mfd/wm831x-spi.c:26

 26static int wm831x_spi_probe(struct spi_device *spi)
 27{
 28        struct wm831x_pdata *pdata = dev_get_platdata(&spi->dev);
 29        const struct spi_device_id *id = spi_get_device_id(spi);
 30        const struct of_device_id *of_id;
 31        struct wm831x *wm831x;
 32        enum wm831x_parent type;
 33        int ret;
 34
 35        if (spi->dev.of_node) {
 36                of_id = of_match_device(wm831x_of_match, &spi->dev);
 37                type = (enum wm831x_parent)of_id->data;
 38        } else {
 39                type = (enum wm831x_parent)id->driver_data;
 40        }
 41
 42        wm831x = devm_kzalloc(&spi->dev, sizeof(struct wm831x),  
GFP_KERNEL);
 43        if (wm831x == NULL)
 44                return -ENOMEM;
 45
 46        spi->mode = SPI_MODE_0;
 47
 48        spi_set_drvdata(spi, wm831x);
 49        wm831x->dev = &spi->dev;
 50        wm831x->type = type;
 51
 52        wm831x->regmap = devm_regmap_init_spi(spi, &wm831x_regmap_config);
 53        if (IS_ERR(wm831x->regmap)) {
 54                ret = PTR_ERR(wm831x->regmap);
 55                dev_err(wm831x->dev, "Failed to allocate register  
map: %d\n",
 56                        ret);
 57                return ret;
 58        }
 59
 60        if (pdata)
 61                memcpy(&wm831x->pdata, pdata, sizeof(*pdata));
 62
 63        return wm831x_device_init(wm831x, spi->irq);
 64}

The issue here is that there is a potential NULL pointer dereference  
at line 37, in case function of_match_device() returns NULL.

Maybe a patch like the following could be applied in order to avoid  
any chance of a NULL pointer dereference:

index c332e28..7b227c9 100644
--- a/drivers/mfd/wm831x-spi.c
+++ b/drivers/mfd/wm831x-spi.c
@@ -34,6 +34,10 @@ static int wm831x_spi_probe(struct spi_device *spi)

        if (spi->dev.of_node) {
                of_id = of_match_device(wm831x_of_match, &spi->dev);
+               if (!of_id) {
+                       dev_err(&spi->dev, "Failed to find matching id\n");
+                       return -EINVAL;
+               }
                type = (enum wm831x_parent)of_id->data;
        } else {
                type = (enum wm831x_parent)id->driver_data;

What do you think?

I'd really appreciate any comment on this.

Thank you!
--
Gustavo A. R. Silva