linux-kernel - Re: [PATCH V2] usb: misc: ljca: Fix double free in error handling path

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Message-ID: <36e56422-d027-4edd-af6e-8ebcebc1dfe3@redhat.com>
Date: Sun, 10 Mar 2024 12:46:22 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: Yongzhi Liu <hyperlyzcs@...il.com>, wentong.wu@...el.com,
 gregkh@...uxfoundation.org, andi.shyti@...ux.intel.com
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
 jitxie@...cent.com, huntazhang@...cent.com
Subject: Re: [PATCH V2] usb: misc: ljca: Fix double free in error handling
 path

Hi Yongzhi Liu,

On 3/7/24 12:57, Yongzhi Liu wrote:
> When auxiliary_device_add() returns error and then calls
> auxiliary_device_uninit(), callback function ljca_auxdev_release
> calls kfree(auxdev->dev.platform_data) to free the parameter data
> of the function ljca_new_client_device. The callers of
> ljca_new_client_device shouldn't call kfree() again
> in the error handling path to free the platform data.
> 
> Fix this by cleaning up the redundant kfree() in all callers and
> adding kfree() the passed in platform_data on errors which happen
> before auxiliary_device_init() succeeds .
> 
> Fixes: acd6199f195d ("usb: Add support for Intel LJCA device")
> Signed-off-by: Yongzhi Liu <hyperlyzcs@...il.com>
> ---
>  drivers/usb/misc/usb-ljca.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/usb/misc/usb-ljca.c b/drivers/usb/misc/usb-ljca.c
> index 35770e608c64..bd9ccbea6e72 100644
> --- a/drivers/usb/misc/usb-ljca.c
> +++ b/drivers/usb/misc/usb-ljca.c
> @@ -518,8 +518,10 @@ static int ljca_new_client_device(struct ljca_adapter *adap, u8 type, u8 id,
>  	int ret;
>  
>  	client = kzalloc(sizeof *client, GFP_KERNEL);
> -	if (!client)
> +	if (!client) {
> +		kfree(data);
>  		return -ENOMEM;
> +	}
>  
>  	client->type = type;
>  	client->id = id;
> @@ -535,8 +537,10 @@ static int ljca_new_client_device(struct ljca_adapter *adap, u8 type, u8 id,
>  	auxdev->dev.release = ljca_auxdev_release;
>  
>  	ret = auxiliary_device_init(auxdev);
> -	if (ret)
> +	if (ret) {
> +		kfree(data);
>  		goto err_free;
> +	}
>  
>  	ljca_auxdev_acpi_bind(adap, auxdev, adr, id);
>  
> @@ -590,12 +594,8 @@ static int ljca_enumerate_gpio(struct ljca_adapter *adap)
>  		valid_pin[i] = get_unaligned_le32(&desc->bank_desc[i].valid_pins);
>  	bitmap_from_arr32(gpio_info->valid_pin_map, valid_pin, gpio_num);
>  
> -	ret = ljca_new_client_device(adap, LJCA_CLIENT_GPIO, 0, "ljca-gpio",
> +	return ljca_new_client_device(adap, LJCA_CLIENT_GPIO, 0, "ljca-gpio",
>  				     gpio_info, LJCA_GPIO_ACPI_ADR);
> -	if (ret)
> -		kfree(gpio_info);
> -
> -	return ret;
>  }
>  
>  static int ljca_enumerate_i2c(struct ljca_adapter *adap)
> @@ -626,13 +626,9 @@ static int ljca_enumerate_i2c(struct ljca_adapter *adap)
>  		i2c_info->capacity = desc->info[i].capacity;
>  		i2c_info->intr_pin = desc->info[i].intr_pin;
>  
> -		ret = ljca_new_client_device(adap, LJCA_CLIENT_I2C, i,
> +		return ljca_new_client_device(adap, LJCA_CLIENT_I2C, i,
>  					     "ljca-i2c", i2c_info,
>  					     LJCA_I2C1_ACPI_ADR + i);
> -		if (ret) {
> -			kfree(i2c_info);
> -			return ret;
> -		}

This is in a for loop, by using:

		return ljca_new_client_device(...);

you are now only creating the first ljca-i2c controller, while
there may be more instead just drop the kfree() from the if (ret) {}
block:

		ret = ljca_new_client_device(...);
		if (ret)
			return ret;

Sorry for not noticing this with the v1 posting.

>  	}
>  
>  	return 0;
> @@ -666,13 +662,9 @@ static int ljca_enumerate_spi(struct ljca_adapter *adap)
>  		spi_info->id = desc->info[i].id;
>  		spi_info->capacity = desc->info[i].capacity;
>  
> -		ret = ljca_new_client_device(adap, LJCA_CLIENT_SPI, i,
> +		return ljca_new_client_device(adap, LJCA_CLIENT_SPI, i,
>  					     "ljca-spi", spi_info,
>  					     LJCA_SPI1_ACPI_ADR + i);
> -		if (ret) {
> -			kfree(spi_info);
> -			return ret;
> -		}
>  	}

Same remark as with the creation of the i2c controllers, please use:

		ret = ljca_new_client_device(...);
		if (ret)
			return ret;

Regards,

Hans