linux-kernel - Re: [PATCH] power: supply: cpcap-battery: fix invalid usage of list cursor

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Date:   Tue, 20 Apr 2021 16:13:03 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     zhuguangqing83@...il.com
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH] power: supply: cpcap-battery: fix invalid usage of list
 cursor

[+Cc Tony]

Hi,

On Wed, Apr 14, 2021 at 02:47:24PM +0800, zhuguangqing83@...il.com wrote:
> From: Guangqing Zhu <zhuguangqing83@...il.com>
>
> Fix invalid usage of a list_for_each_entry in cpcap_battery_irq_thread().
> When list is empty or if the list is completely traversed (without breaking
> from the loop on one of the entries) then the list cursor does not point
> to a valid entry and therefore should not be used. "if (!d)" will never
> happen, maybe we should use "if (&d->node == &ddata->irq_list)".

Commit message does not make sense. I think you meant to say:

Empty list or fully traversed list points to list head, which is not
NULL (and before the first element containing real data).

> Fixes: 874b2adbed125 ("power: supply: cpcap-battery: Add a battery driver")
> Signed-off-by: Guangqing Zhu <zhuguangqing83@...il.com>
> ---
>  drivers/power/supply/cpcap-battery.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/power/supply/cpcap-battery.c b/drivers/power/supply/cpcap-battery.c
> index 6d5bcdb9f45d..8169dc71a786 100644
> --- a/drivers/power/supply/cpcap-battery.c
> +++ b/drivers/power/supply/cpcap-battery.c
> @@ -786,7 +786,7 @@ static irqreturn_t cpcap_battery_irq_thread(int irq, void *data)
>  			break;
>  	}
>  
> -	if (!d)
> +	if (&d->node == &ddata->irq_list)
>  		return IRQ_NONE;

Please use list_entry_is_head() instead of open coding it.

>  	latest = cpcap_battery_latest(ddata);

Thanks,

-- Sebastian

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