linux-kernel - Re: [PATCH v3] backlight: pm8941: Add NULL check in wled

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Message-ID: <Z-uqpxcge0J99IPI@aspen.lan>
Date: Tue, 1 Apr 2025 09:58:15 +0100
From: Daniel Thompson <danielt@...nel.org>
To: Henry Martin <bsdhenrymartin@...il.com>
Cc: Markus.Elfring@....de, lee@...nel.org, jingoohan1@...il.com,
	deller@....de, linux-arm-msm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH v3] backlight: pm8941: Add NULL check in wled_configure()

On Tue, Apr 01, 2025 at 04:29:50PM +0800, Henry Martin wrote:
> The function wled_configure() uses devm_kasprintf() without checking for
> allocation failures, which could lead to NULL pointer dereferences.
>
> Add proper error handling when devm_kasprintf() fails by:
> - Returning -ENOMEM immediately
> - Ensuring no resources are left allocated (none need cleanup in this case)

Two things have gone wrong here:

1. This patch has been incorrectly posted with the wrong patch number.
2. You've let Markus bully you into adding some pointless text in the
   patch description ;-). I think the original v3 was better worded.
   IMHO the bulleted list adds nothing useful.

When you get the chance please send a v4 of the patch so we can pick it
up without any confusion (I suspect it might be a week or two before
this gets pulled so clean mail threads help a lot). It's up to you but
I'd recommend keeping the original v3 wording and label it something
like:
V3 -> V4: No functional changes, just correcting the version number


Daniel.



>
> Fixes: f86b77583d88 ("backlight: pm8941: Convert to using %pOFn instead of device_node.name")
> Signed-off-by: Henry Martin <bsdhenrymartin@...il.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> ---
> V2 -> V3: Fix commit message and verify proper error handling with
> resource cleanup.
> V1 -> V2: Fix commit message to use imperative mood and wrap lines to 75
> characters.
>
>  drivers/video/backlight/qcom-wled.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 9afe701b2a1b..a63bb42c8f8b 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -1406,9 +1406,11 @@ static int wled_configure(struct wled *wled)
>  	wled->ctrl_addr = be32_to_cpu(*prop_addr);
>
>  	rc = of_property_read_string(dev->of_node, "label", &wled->name);
> -	if (rc)
> +	if (rc) {
>  		wled->name = devm_kasprintf(dev, GFP_KERNEL, "%pOFn", dev->of_node);
> -
> +		if (!wled->name)
> +			return -ENOMEM;
> +	}
>  	switch (wled->version) {
>  	case 3:
>  		u32_opts = wled3_opts;
> --
> 2.34.1
>