Re: [rft, PATCH v5 1/1] gpiolib: fix memory leak in gpiochip_setup_dev()

[Zeng Heng <zengheng4@huawei.com>]

On 2022/11/19 3:45, Andy Shevchenko wrote:
> From: Zeng Heng <zengheng4@huawei.com>
>
> Here is a backtrace report about memory leak detected in
> gpiochip_setup_dev():
>
> unreferenced object 0xffff88810b406400 (size 512):
>    comm "python3", pid 1682, jiffies 4295346908 (age 24.090s)
>    backtrace:
>      kmalloc_trace
>      device_add		device_private_init at drivers/base/core.c:3361
> 			(inlined by) device_add at drivers/base/core.c:3411
>      cdev_device_add
>      gpiolib_cdev_register
>      gpiochip_setup_dev
>      gpiochip_add_data_with_key
>
> gcdev_register() & gcdev_unregister() would call device_add() &
> device_del() (no matter CONFIG_GPIO_CDEV is enabled or not) to
> register/unregister device.
>
> However, if device_add() succeeds, some resource (like
> struct device_private allocated by device_private_init())
> is not released by device_del().
>
> Therefore, after device_add() succeeds by gcdev_register(), it
> needs to call put_device() to release resource in the error handle
> path.
>
> Here we move forward the register of release function, and let it
> release every piece of resource by put_device() instead of kfree().
>
> While at it, fix another subtle issue, i.e. when gc->ngpio is equal
> to 0, we still call kcalloc() and, in case of further error, kfree()
> on the ZERO_PTR pointer, which is not NULL. It's not a bug per se,
> but rather waste of the resources and potentially wrong expectation
> about contents of the gdev->descs variable.
>
> Fixes: 159f3cd92f17 ("gpiolib: Defer gpio device setup until after gpiolib initialization")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> Co-developed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> changes in v5 (done by Andy):
>    - refactored to avoid double checks on the same conditionals
>    - moved kcalloc() after validating its parameter
>    - compiled tested only by me (Andy)

I have applied the patch on local environment, and it works fine after 
rough test

(which is based on QEMU simulated).

Best regards,

Zeng Heng

> changes in v4:
>    - add gpiochip_print_register_fail()
> changes in v3:
>    - use put_device() instead of kfree() explicitly
> changes in v2:
>    - correct fixes tag
>
>   drivers/gpio/gpiolib.c | 42 ++++++++++++++++++++++++++----------------
>   1 file changed, 26 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index caa747fdcb72..119c9c3a2a50 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -580,12 +580,13 @@ static int gpiochip_setup_dev(struct gpio_device *gdev)
>   	if (ret)
>   		return ret;
>   
> +	/* From this point, the .release() function cleans up gpio_device */
> +	gdev->dev.release = gpiodevice_release;
> +
>   	ret = gpiochip_sysfs_register(gdev);
>   	if (ret)
>   		goto err_remove_device;
>   
> -	/* From this point, the .release() function cleans up gpio_device */
> -	gdev->dev.release = gpiodevice_release;
>   	dev_dbg(&gdev->dev, "registered GPIOs %d to %d on %s\n", gdev->base,
>   		gdev->base + gdev->ngpio - 1, gdev->chip->label ? : "generic");
>   
> @@ -651,10 +652,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	struct fwnode_handle *fwnode = NULL;
>   	struct gpio_device *gdev;
>   	unsigned long flags;
> -	int base = gc->base;
>   	unsigned int i;
> +	u32 ngpios = 0;
> +	int base = 0;
>   	int ret = 0;
> -	u32 ngpios;
>   
>   	/* If the calling driver did not initialize firmware node, do it here */
>   	if (gc->fwnode)
> @@ -696,17 +697,12 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	else
>   		gdev->owner = THIS_MODULE;
>   
> -	gdev->descs = kcalloc(gc->ngpio, sizeof(gdev->descs[0]), GFP_KERNEL);
> -	if (!gdev->descs) {
> -		ret = -ENOMEM;
> -		goto err_free_dev_name;
> -	}
> -
>   	/*
>   	 * Try the device properties if the driver didn't supply the number
>   	 * of GPIO lines.
>   	 */
> -	if (gc->ngpio == 0) {
> +	ngpios = gc->ngpio;
> +	if (ngpios == 0) {
>   		ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
>   		if (ret == -ENODATA)
>   			/*
> @@ -717,7 +713,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   			 */
>   			ngpios = 0;
>   		else if (ret)
> -			goto err_free_descs;
> +			goto err_free_dev_name;
>   
>   		gc->ngpio = ngpios;
>   	}
> @@ -725,13 +721,19 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	if (gc->ngpio == 0) {
>   		chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
>   		ret = -EINVAL;
> -		goto err_free_descs;
> +		goto err_free_dev_name;
>   	}
>   
>   	if (gc->ngpio > FASTPATH_NGPIO)
>   		chip_warn(gc, "line cnt %u is greater than fast path cnt %u\n",
>   			  gc->ngpio, FASTPATH_NGPIO);
>   
> +	gdev->descs = kcalloc(gc->ngpio, sizeof(*gdev->descs), GFP_KERNEL);
> +	if (!gdev->descs) {
> +		ret = -ENOMEM;
> +		goto err_free_dev_name;
> +	}
> +
>   	gdev->label = kstrdup_const(gc->label ?: "unknown", GFP_KERNEL);
>   	if (!gdev->label) {
>   		ret = -ENOMEM;
> @@ -750,11 +752,13 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	 * it may be a pipe dream. It will not happen before we get rid
>   	 * of the sysfs interface anyways.
>   	 */
> +	base = gc->base;
>   	if (base < 0) {
>   		base = gpiochip_find_base(gc->ngpio);
>   		if (base < 0) {
> -			ret = base;
>   			spin_unlock_irqrestore(&gpio_lock, flags);
> +			ret = base;
> +			base = 0;
>   			goto err_free_label;
>   		}
>   		/*
> @@ -868,6 +872,11 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   err_free_gpiochip_mask:
>   	gpiochip_remove_pin_ranges(gc);
>   	gpiochip_free_valid_mask(gc);
> +	if (gdev->dev.release) {
> +		/* release() has been registered by gpiochip_setup_dev() */
> +		put_device(&gdev->dev);
> +		goto err_print_message;
> +	}
>   err_remove_from_list:
>   	spin_lock_irqsave(&gpio_lock, flags);
>   	list_del(&gdev->list);
> @@ -881,13 +890,14 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   err_free_ida:
>   	ida_free(&gpio_ida, gdev->id);
>   err_free_gdev:
> +	kfree(gdev);
> +err_print_message:
>   	/* failures here can mean systems won't boot... */
>   	if (ret != -EPROBE_DEFER) {
>   		pr_err("%s: GPIOs %d..%d (%s) failed to register, %d\n", __func__,
> -		       gdev->base, gdev->base + gdev->ngpio - 1,
> +		       base, base + (int)ngpios - 1,
>   		       gc->label ? : "generic", ret);
>   	}
> -	kfree(gdev);
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(gpiochip_add_data_with_key);