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

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

[zhuguangqing83]

From: Guangqing Zhu <zhuguangqing83@gmail.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)".

Fixes: 874b2adbed125 ("power: supply: cpcap-battery: Add a battery driver")
Signed-off-by: Guangqing Zhu <zhuguangqing83@gmail.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;
 
 	latest = cpcap_battery_latest(ddata);
-- 
2.17.1

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

[Sebastian Reichel]

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[+Cc Tony]

Hi,

On Wed, Apr 14, 2021 at 02:47:24PM +0800, zhuguangqing83@gmail.com wrote:
> From: Guangqing Zhu <zhuguangqing83@gmail.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@gmail.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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