backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

[PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Christophe JAILLET 4 years, 4 months ago

kmalloc_array()/kcalloc() should be used to avoid potential overflow when
a multiplication is needed to compute the size of the requested memory.

So turn a kzalloc()+explicit size computation into an equivalent kcalloc().

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/video/backlight/pwm_bl.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 8d8959a70e44..c0523a0269ee 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -263,9 +263,8 @@ static int pwm_backlight_parse_dt(struct device *dev,
 
 	/* read brightness levels from DT property */
 	if (num_levels > 0) {
-		size_t size = sizeof(*data->levels) * num_levels;
-
-		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
+		data->levels = devm_kcalloc(dev, num_levels,
+					    sizeof(*data->levels), GFP_KERNEL);
 		if (!data->levels)
 			return -ENOMEM;
 
@@ -320,8 +319,8 @@ static int pwm_backlight_parse_dt(struct device *dev,
 			 * Create a new table of brightness levels with all the
 			 * interpolated steps.
 			 */
-			size = sizeof(*table) * num_levels;
-			table = devm_kzalloc(dev, size, GFP_KERNEL);
+			table = devm_kcalloc(dev, num_levels, sizeof(*table),
+					     GFP_KERNEL);
 			if (!table)
 				return -ENOMEM;
 			/*
-- 
2.32.0

Re: [PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Uwe Kleine-König 4 years, 4 months ago

On Sat, Feb 05, 2022 at 08:40:48AM +0100, Christophe JAILLET wrote:
> kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> a multiplication is needed to compute the size of the requested memory.
> 
> So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

LGTM

Acked-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

Re: [PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Lee Jones 4 years, 4 months ago

On Mon, 07 Feb 2022, Uwe Kleine-König wrote:

> On Sat, Feb 05, 2022 at 08:40:48AM +0100, Christophe JAILLET wrote:
> > kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> > a multiplication is needed to compute the size of the requested memory.
> > 
> > So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
> > 
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> 
> LGTM
> 
> Acked-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> 
> Thanks
> Uwe

I am totally confused!

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Uwe Kleine-König 4 years, 4 months ago

On Mon, Feb 07, 2022 at 09:31:00AM +0000, Lee Jones wrote:
> On Mon, 07 Feb 2022, Uwe Kleine-König wrote:
> 
> > On Sat, Feb 05, 2022 at 08:40:48AM +0100, Christophe JAILLET wrote:
> > > kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> > > a multiplication is needed to compute the size of the requested memory.
> > > 
> > > So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
> > > 
> > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > 
> > LGTM
> > 
> > Acked-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > 
> > Thanks
> > Uwe
> 
> I am totally confused!

An rightfully so. Copy-paste-fail, this was supposed to be

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Sorry!

Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

Re: [PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Daniel Thompson 4 years, 4 months ago

On Sat, Feb 05, 2022 at 08:40:48AM +0100, Christophe JAILLET wrote:
> kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> a multiplication is needed to compute the size of the requested memory.
> 
> So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH] backlight: pwm_bl: Avoid open coded arithmetic in memory allocation

Posted by Lee Jones 4 years, 4 months ago

On Sat, 05 Feb 2022, Christophe JAILLET wrote:

> kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> a multiplication is needed to compute the size of the requested memory.
> 
> So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/video/backlight/pwm_bl.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog