linux-kernel - Re: [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT

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Date:   Tue, 5 Oct 2021 10:14:52 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     phone-devel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Kiran Gunda <kgunda@...eaurora.org>,
        Courtney Cavin <courtney.cavin@...ymobile.com>,
        Bryan Wu <cooloney@...il.com>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/10] backlight: qcom-wled: Validate enabled string
 indices in DT

On Mon, Oct 04, 2021 at 09:27:35PM +0200, Marijn Suijten wrote:
> The strings passed in DT may possibly cause out-of-bounds register
> accesses and should be validated before use.
> 
> Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")

The first half of this patch actually fixes patch 1 from this patch set.
It would be better to move that code there.


Daniel.


> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> ---
>  drivers/video/backlight/qcom-wled.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 29910e603c42..27e8949c7922 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -1526,6 +1526,12 @@ static int wled_configure(struct wled *wled)
>  						     "qcom,enabled-strings",
>  						     sizeof(u32));
>  	if (string_len > 0) {
> +		if (string_len > wled->max_string_count) {
> +			dev_err(dev, "Cannot have more than %d strings\n",
> +				wled->max_string_count);
> +			return -EINVAL;
> +		}
> +
>  		rc = of_property_read_u32_array(dev->of_node,
>  						"qcom,enabled-strings",
>  						wled->cfg.enabled_strings,
> @@ -1537,6 +1543,14 @@ static int wled_configure(struct wled *wled)
>  			return -EINVAL;
>  		}
>  
> +		for (i = 0; i < string_len; ++i) {
> +			if (wled->cfg.enabled_strings[i] >= wled->max_string_count) {
> +				dev_err(dev, "qcom,enabled-strings index %d at %d is out of bounds\n",
> +					wled->cfg.enabled_strings[i], i);
> +				return -EINVAL;
> +			}
> +		}
> +
>  		cfg->num_strings = string_len;
>  	}
>  
> -- 
> 2.33.0
>