linux-kernel - Re: [PATCH] drm/nouveau/therm: Fix pointer dereferenced before checking

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Date:   Tue, 31 May 2022 09:38:03 +0800
From:   baihaowen <baihaowen@...zu.com>
To:     Ben Skeggs <bskeggs@...hat.com>, Karol Herbst <kherbst@...hat.com>,
        "Lyude Paul" <lyude@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
CC:     <dri-devel@...ts.freedesktop.org>, <nouveau@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/nouveau/therm: Fix pointer dereferenced before
 checking


在 2022/5/30 上午11:10, Haowen Bai 写道:
> The fan->base is dereferencing before null checking, so move
> it after checking.
>
> Signed-off-by: Haowen Bai <baihaowen@...zu.com>
> ---
>  drivers/gpu/drm/nouveau/nvkm/subdev/therm/fanpwm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/therm/fanpwm.c b/drivers/gpu/drm/nouveau/nvkm/subdev/therm/fanpwm.c
> index 340f37a299dc..b13ba9b2f6be 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/therm/fanpwm.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/therm/fanpwm.c
> @@ -98,10 +98,10 @@ nvkm_fanpwm_create(struct nvkm_therm *therm, struct dcb_gpio_func *func)
>  		return -ENODEV;
>  
>  	fan = kzalloc(sizeof(*fan), GFP_KERNEL);
> -	therm->fan = &fan->base;
>  	if (!fan)
>  		return -ENOMEM;
>  
> +	therm->fan = &fan->base;
>  	fan->base.type = "PWM";
>  	fan->base.get = nvkm_fanpwm_get;
>  	fan->base.set = nvkm_fanpwm_set;
Sorry, plz ignore this patch.

fan->base is dereferenced, &fan->base is just a pointer math for pointer address offset, so it would not cause a bug(dereferencing null pointer).

 

-- 
Haowen Bai