linux-kernel - Re: [PATCH] power: supply: fix memory leaks

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Message-ID: <20200502223942.fksizdglrw5zdpw6@earth.universe>
Date:   Sun, 3 May 2020 00:39:42 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     wu000273@....edu
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kjlu@....edu, Andrey Smirnov <andrew.smirnov@...il.com>
Subject: Re: [PATCH] power: supply: fix memory leaks

Hi,

On Sat, May 02, 2020 at 04:10:56PM -0500, wu000273@....edu wrote:
> From: Qiushi Wu <wu000273@....edu>
> 
> In function power_supply_add_hwmon_sysfs(), psyhw->props is
> allocated by bitmap_zalloc(). But this pointer is not deallocated
> in several error paths, which lead to memory leak bugs. To fix
> this, we can call bitmap_free() to free this pointer.
> 
> Signed-off-by: Qiushi Wu <wu000273@....edu>
> ---

You are correct, that there is a problem in the first instance, but
the other changes are incorrect and introduce a new double free. Please
read documentation for devm_add_action(). The proper fix is to just
replace the call to devm_add_action() with devm_add_action_or_reset().
Please send a new version for this. Also please add the following
tag:

Fixes: e67d4dfc9ff19 ("power: supply: Add HWMON compatibility layer")

Thanks,

-- Sebastian

>  drivers/power/supply/power_supply_hwmon.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/power/supply/power_supply_hwmon.c b/drivers/power/supply/power_supply_hwmon.c
> index 75cf861ba492..7453390ab7a4 100644
> --- a/drivers/power/supply/power_supply_hwmon.c
> +++ b/drivers/power/supply/power_supply_hwmon.c
> @@ -307,7 +307,7 @@ int power_supply_add_hwmon_sysfs(struct power_supply *psy)
>  	ret = devm_add_action(dev, power_supply_hwmon_bitmap_free,
>  			      psyhw->props);
>  	if (ret)
> -		goto error;
> +		goto out_free;
>  
>  	for (i = 0; i < desc->num_properties; i++) {
>  		const enum power_supply_property prop = desc->properties[i];
> @@ -342,7 +342,7 @@ int power_supply_add_hwmon_sysfs(struct power_supply *psy)
>  		new_name = devm_kstrdup(dev, name, GFP_KERNEL);
>  		if (!new_name) {
>  			ret = -ENOMEM;
> -			goto error;
> +			goto out_free;
>  		}
>  		strreplace(new_name, '-', '_');
>  		name = new_name;
> @@ -353,10 +353,12 @@ int power_supply_add_hwmon_sysfs(struct power_supply *psy)
>  						NULL);
>  	ret = PTR_ERR_OR_ZERO(hwmon);
>  	if (ret)
> -		goto error;
> +		goto out_free;
>  
>  	devres_close_group(dev, power_supply_add_hwmon_sysfs);
>  	return 0;
> +out_free:
> +	bitmap_free(psyhw->props);
>  error:
>  	devres_release_group(dev, NULL);
>  	return ret;
> -- 
> 2.17.1
> 

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