mfd: max77693: Fix possible NULL pointer dereference on i2c_new_dummy error

During probe the driver allocates dummy I2C devices for MUIC and haptic
with i2c_new_dummy() but it does not check the return value of this
calls.

In case of error (i2c_new_device(): memory allocation failure or I2C
address cannot be used) this function returns NULL which is later used
by devm_regmap_init_i2c() and i2c_unregister_device().

If i2c_new_dummy() fails for MUIC or haptic devices, fail also the probe
for main MFD driver.

Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/max77693.c

@@ -148,9 +148,18 @@ static int max77693_i2c_probe(struct i2c_client *i2c,
 		dev_info(max77693->dev, "device ID: 0x%x\n", reg_data);
 
 	max77693->muic = i2c_new_dummy(i2c->adapter, I2C_ADDR_MUIC);
+	if (!max77693->muic) {
+		dev_err(max77693->dev, "Failed to allocate I2C device for MUIC\n");
+		return -ENODEV;
+	}
 	i2c_set_clientdata(max77693->muic, max77693);
 
 	max77693->haptic = i2c_new_dummy(i2c->adapter, I2C_ADDR_HAPTIC);
+	if (!max77693->haptic) {
+		dev_err(max77693->dev, "Failed to allocate I2C device for Haptic\n");
+		ret = -ENODEV;
+		goto err_i2c_haptic;
+	}
 	i2c_set_clientdata(max77693->haptic, max77693);
 
 	/*
@@ -184,8 +193,9 @@ static int max77693_i2c_probe(struct i2c_client *i2c,
 	max77693_irq_exit(max77693);
 err_irq:
 err_regmap_muic:
-	i2c_unregister_device(max77693->muic);
 	i2c_unregister_device(max77693->haptic);
+err_i2c_haptic:
+	i2c_unregister_device(max77693->muic);
 	return ret;
 }