kasprintf() may return NULL on failure of internal allocation thus the
assigned  label  is not safe if not explicitly checked. On error
mediatek_gpio_bank_probe() returns negative values so -ENOMEM in the
(unlikely) failure case should be fine here.

Signed-off-by: Nicholas Mc Guire <redacted>
Fixes: 4ba9c3afda41 ("gpio: mt7621: Add a driver for MT7621")
---

V2: The dev_err() for the unlikely case of the devm_kasprintf()
    failing was removed on request from Bartosz Golaszewski
    [off-list ref]

Problem located with experimental coccinelle script

Patch was compile tested with: omega2p_defconfig, SOC_MT7621=y,
GPIOLIB=y, GPIO_MT7621=y

Patch is against 4.20-rc3 (localversion-next is next-20181121)

 drivers/gpio/gpio-mt7621.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
index d72af6f..1ec95bc 100644
--- a/drivers/gpio/gpio-mt7621.c
+++ b/drivers/gpio/gpio-mt7621.c

@@ -244,6 +244,8 @@ mediatek_gpio_bank_probe(struct device *dev,
        rg->chip.of_xlate = mediatek_gpio_xlate;
        rg->chip.label = devm_kasprintf(dev, GFP_KERNEL, "%s-bank%d",
                                        dev_name(dev), bank);
+       if (!rg->chip.label)
+               return -ENOMEM;

        ret = devm_gpiochip_add_data(dev, &rg->chip, mtk);
        if (ret < 0) {
--

2.1.4