linux-kernel - Re: [PATCH] platform/x86: fujitsu-laptop: add NULL check on devm

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Message-ID: <20170707001900.GE6573@marvin.atrad.com.au>
Date:   Fri, 7 Jul 2017 09:49:00 +0930
From:   Jonathan Woithe <jwoithe@...t42.net>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: fujitsu-laptop: add NULL check on
 devm_kzalloc() return value

On Thu, Jul 06, 2017 at 05:19:02PM -0500, Gustavo A. R. Silva wrote:
> Check return value from call to devm_kzalloc()
> in order to prevent a NULL pointer dereference.
> 
> This issue was detected using Coccinelle and the following semantic patch:
> 
> @@
> expression x;
> identifier fld;
> @@
> 
> * x = devm_kzalloc(...);
>   ... when != x == NULL
>   x->fld
> 
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>

These checks should be added in the interest of code correctness. 
devm_kzalloc() can fail (even if it's extremely unlikely in practice) so we
should check for this.

Reviewed-by: Jonathan Woithe <jwoithe@...t42.net>

> ---
>  drivers/platform/x86/fujitsu-laptop.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
> index c1a8528..593a350 100644
> --- a/drivers/platform/x86/fujitsu-laptop.c
> +++ b/drivers/platform/x86/fujitsu-laptop.c
> @@ -695,6 +695,9 @@ static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
>  	if (call_fext_func(device,
>  			   FUNC_LEDS, 0x0, 0x0, 0x0) & LOGOLAMP_POWERON) {
>  		led = devm_kzalloc(&device->dev, sizeof(*led), GFP_KERNEL);
> +		if (!led)
> +			return -ENOMEM;
> +
>  		led->name = "fujitsu::logolamp";
>  		led->brightness_set_blocking = logolamp_set;
>  		led->brightness_get = logolamp_get;
> @@ -707,6 +710,9 @@ static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
>  			    FUNC_LEDS, 0x0, 0x0, 0x0) & KEYBOARD_LAMPS) &&
>  	    (call_fext_func(device, FUNC_BUTTONS, 0x0, 0x0, 0x0) == 0x0)) {
>  		led = devm_kzalloc(&device->dev, sizeof(*led), GFP_KERNEL);
> +		if (!led)
> +			return -ENOMEM;
> +
>  		led->name = "fujitsu::kblamps";
>  		led->brightness_set_blocking = kblamps_set;
>  		led->brightness_get = kblamps_get;
> @@ -723,6 +729,9 @@ static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
>  	 */
>  	if (call_fext_func(device, FUNC_BUTTONS, 0x0, 0x0, 0x0) & BIT(24)) {
>  		led = devm_kzalloc(&device->dev, sizeof(*led), GFP_KERNEL);
> +		if (!led)
> +			return -ENOMEM;
> +
>  		led->name = "fujitsu::radio_led";
>  		led->brightness_set_blocking = radio_led_set;
>  		led->brightness_get = radio_led_get;
> @@ -741,6 +750,9 @@ static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
>  	    (call_fext_func(device,
>  			    FUNC_LEDS, 0x2, ECO_LED, 0x0) != UNSUPPORTED_CMD)) {
>  		led = devm_kzalloc(&device->dev, sizeof(*led), GFP_KERNEL);
> +		if (!led)
> +			return -ENOMEM;
> +
>  		led->name = "fujitsu::eco_led";
>  		led->brightness_set_blocking = eco_led_set;
>  		led->brightness_get = eco_led_get;
> -- 
> 2.5.0