linux-kernel - Re: [PATCH next] drm/fsl-dcu: prevent error pointer dereference in fsl_dcu

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Message-ID: <e45a5f9a63e6dba8eb57bac3c5001e8a360af393.camel@ew.tq-group.com>
Date: Wed, 23 Oct 2024 11:26:24 +0200
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Stefan Agner <stefan@...er.ch>, Alison Wang <alison.wang@....com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Dmitry Baryshkov
 <dmitry.baryshkov@...aro.org>, Alexander Stein
 <alexander.stein@...tq-group.com>, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH next] drm/fsl-dcu: prevent error pointer dereference in
 fsl_dcu_load()

On Wed, 2024-10-23 at 11:35 +0300, Dan Carpenter wrote:
> 
> The syscon_regmap_lookup_by_compatible() function returns -ENODEV if
> there isn't a compatible for it or other error pointers on error.  This
> code only checks for -ENODEV instead of checking for other errors so it
> could lead to an error pointer dereference inside the regmap_update_bits()
> function.
> 
> Fixes: ffcde9e44d3e ("drm: fsl-dcu: enable PIXCLK on LS1021A")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Reviewed-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>



> ---
>  drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> index 91a48d774cf7..5997d9b4a431 100644
> --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
> @@ -109,7 +109,9 @@ static int fsl_dcu_load(struct drm_device *dev, unsigned long flags)
>  		return dev_err_probe(dev->dev, ret, "failed to initialize mode setting\n");
>  
>  	scfg = syscon_regmap_lookup_by_compatible("fsl,ls1021a-scfg");
> -	if (PTR_ERR(scfg) != -ENODEV) {
> +	if (IS_ERR(scfg) && PTR_ERR(scfg) != -ENODEV)
> +		return dev_err_probe(dev->dev, PTR_ERR(scfg), "failed to find regmap\n");
> +	if (!IS_ERR(scfg)) {
>  		/*
>  		 * For simplicity, enable the PIXCLK unconditionally,
>  		 * resulting in increased power consumption. Disabling

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